Papermaking belt and method of making the same using differential light transmission techniques

ABSTRACT

A backside textured papermaking belt is disclosed which is comprised of a framework and a reinforcing structure. The framework has a first surface which defines the paper-contacting side of the belt, a second surface opposite the first surface, and conduits which extend between first and second surfaces of the belt. The first surface of the framework has a paper side network formed therein which defines the conduits. The second surface of the framework has a backside network with passageways that provide surface texture irregularities in the backside network. The papermaking belt is made by applying a coating of photosensitive resinous material to a reinforcing structure which has opaque portions, and then exposing the photosensitive resinous material to light of an activating wavelength through a mask which has transparent and opaque regions and also through the reinforcing structure. A process for making paper products is also disclosed which involves applying a fluid pressure differential from a vacuum source through the belt to a partially-formed embryonic web of papermaking fibers. The fibers in the embryonic web are deflected into the conduits of the papermaking belt by the vacuum pressure while the papermaking belt and the embryonic web travel over the vacuum source. Following the deflection, the paper web is impressed with the paper side network of the belt, and dried to form the final product.

This is a division of application Ser. No. 07/546,633, filed on Jun. 29,1990, now abandoned.

FIELD OF THE INVENTION

The present invention generally relates to papermaking belts useful inpapermaking machines for making strong, soft, absorbent paper products.This invention is also concerned with a method of making such apapermaking belt and papermaking processes which employ thesepapermaking belts. More particularly, this invention is concerned withpapermaking belts comprised of a resinous framework and a reinforcingstructure which have a texture on their machine-contacting side, orbackside. The texture is imparted to the belt by applying a coating ofphotosensitive resinous material to a reinforcing structure which hasopaque portions, and then exposing the resinous material to light havingan activating wavelength through the reinforcing structure so that theresinous material under the opaque portions of the reinforcing structureremains uncured. The uncured resin is then removed to leave passagewaysin the backside of the belt.

BACKGROUND OF THE INVENTION

One pervasive feature of daily life in modern industrialized societiesis the use of paper products for a variety of purposes. Paper towels,facial tissues, toilet tissue, and the like are in almost constant use.The large demand for such paper products has created a demand forimproved versions of the products and of the methods of theirmanufacture. Despite great strides in paper making, research anddevelopment efforts continue to be aimed at improving both the productsand their processes of manufacture.

Paper products such as paper towels, facial tissues, toilet tissue, andthe like are made from one or more webs of tissue paper. If the productsare to perform their intended tasks and to find wide acceptance, they,and the tissue paper webs from which they are made, must exhibit certainphysical characteristics. Among the more important of thesecharacteristics are strength, softness, and absorbency.

Strength is the ability of a paper web to retain its physical integrityduring use.

Softness is the pleasing tactile sensation one perceives when theycrumple the paper in their hands and when they use the paper for itsintended purposes.

Absorbency is the characteristic of the paper which allows it to take upand retain fluids, particularly water and aqueous solutions andsuspensions. In evaluating the absorbency of paper, not only is theabsolute quantity of fluid a given amount of paper will holdsignificant, but the rate at which the paper will absorb the fluid isalso important. In addition, when the paper is formed into a productsuch as a towel or wipe, the ability of the paper to cause a fluid to betaken up into the paper and thereby leave a dry wiped surface is alsoimportant.

Processes for the manufacturing of paper products for use in tissue,toweling and sanitary products generally involve the preparation of anaqueous slurry of paper fibers and then subsequently removing the waterfrom the slurry while contemporaneously rearranging the fibers in theslurry to form a paper web. Various types of machinery can be employedto assist in the dewatering process.

Currently, most manufacturing processes either employ machines which areknown as Fourdrinier wire papermaking machines or machines which areknown as twin (Fourdrinier) wire papermachines. In Fourdrinier wirepapermaking machines, the paper slurry is fed onto the top surface of atraveling endless belt, which serves as the initial papermaking surfaceof the machine. In twin wire machines, the slurry is deposited between apair of converging Fourdrinier wires in which the initial dewatering andrearranging in the papermaking process are carried out.

After the initial forming of the paper web on the Fourdrinier wire orwires, both types of machines generally carry the paper web through adrying process or processes on another fabric in the form of an endlessbelt which is often different from the Fourdrinier wire or wires. Thisother fabric is sometimes referred to as a drying fabric. Numerousarrangements of the Fourdrinier wire(s) and the drying fabric(s) as wellas the drying process(es) have been used successfully and somewhat lessthan successfully. The drying process(es) can involve mechanicalcompaction of the paper web, vacuum dewatering, drying by blowing heatedair through the paper web, and other types of processes.

As seen above, papermaking belts or fabrics carry various namesdepending on their intended use. Fourdrinier wires, also known asFourdrinier belts, forming wires, or forming fabrics are those which areused in the initial forming zone of the papermaking machine. Dryerfabrics as noted above, are those which carry the paper web through thedrying operation of the papermaking machine. Various other types ofbelts or fabrics are possible also. Most papermaking belts employed inthe past are commonly formed from a length of woven fabric the ends ofwhich have been joined together in a seam to form an endless belt. Wovenpapermaking fabrics generally comprise a plurality of spacedlongitudinal warp threads and a plurality of spaced transverse weftthreads which have been woven together in a specific weaving pattern.Prior belts have included single layer (of warp and weft threads)fabrics, multilayered fabrics, and fabrics with several layers each ofwhich comprises interwoven warp and weft threads. Initially, the threadsof papermaking fabrics were made from wires comprised of materials suchas phosphor bronze, bronze, stainless steel, brass or combinationsthereof. Often various materials were placed on top of and affixed tothe fabrics to attempt to make the dewatering process more efficient.Recently, in the papermaking field, it has been found that syntheticmaterials may be used in whole or part to produce the underlying wirestructures, which are superior in quality to the forming wires made ofmetal threads. Such synthetic materials have included Nylon, polyesters,acrylic fibers and copolymers. While many different processes, fabrics,and arrangements of these fabrics have been used, only certain of theseprocesses, fabrics, and arrangements of these fabrics have resulted incommercially successful paper products.

An example of paper webs which have been widely accepted by theconsuming public are those made by the process described in U.S. Pat.No. 3,301,746 issued to Sanford and Sisson on Jan. 31, 1967. Otherwidely accepted paper products are made by the process described in U.S.Pat. No. 3,994,771 issued to Morgan and Rich on Nov. 30, 1976. Despitethe high quality of products made by these two processes, however, thesearch for still improved products has, as noted above, continued.

Another commercially significant improvement was made upon the abovepaper webs by the process described in U.S. Pat. No. 4,529,480 issued toTrokhan on Jul. 16, 1985, which is incorporated by reference herein. Theimprovement included utilizing a papermaking belt (which was termed a"deflection member") comprised of a foraminous woven member which wassurrounded by a hardened photosensitive resin framework. The resinframework was provided with a plurality of discrete, isolated, channelsknown as "deflection conduits." The process in which this deflectionmember was used involved, among other steps, associating an embryonicweb of papermaking fibers with the top surface of the deflection memberand applying a vacuum or other fluid pressure differential to the webfrom the backside (machine-contacting side) of the deflection member.The papermaking belt used in this process was termed a "deflectionmember" because the papermaking fibers would be deflected into andrearranged into the deflection conduits of the hardened resin frameworkupon the application of the fluid pressure differential. By utilizingthe aforementioned improved papermaking process, as noted below, it wasfinally possible to create paper having certain desired preselectedcharacteristics.

The deflection member described in the aforementioned patent issued toTrokhan was made by the process described in U.S. Pat. No. 4,514,345,issued in the name of Johnson, et al., which is the incorporated byreference herein. The process described in the Johnson, et al. patentincludes the steps of: 1) coating the foraminous woven element with aphotosensitive resin; 2) controlling the thickness of the photosensitiveresin to a preselected value; 3) exposing the resin to a light having anactivating wave length through a mask having opaque and transparentregions; and 4) removing the uncured resin. This process produced adeflection member with a framework which had a paper web-contactingsurface and a machine-contacting surface that were each provided with anetwork pattern surrounding the conduits which was essentiallymonoplanar or smooth.

The paper produced using the process disclosed in U.S. Pat. No.4,529,480 is described in U.S. Pat. No. 4,637,859, issued in the name ofTrokhan, which is incorporated herein by reference. This paper ischaracterized by having two physically distinct regions distributedacross its surfaces. One of the regions is a continuous network regionwhich has a relatively high density and high intrinsic strength. Theother region is one which is comprised of a plurality of domes which arecompletely encircled by the network region. The domes in the latterregion have relatively low densities and relatively low intrinsicstrengths compared to the network region.

The paper produced by the process described in U.S. Pat. No. 4,529,480was actually stronger, softer, and more absorbent than the paperproduced by the preceding processes as a result of several factors. Thestrength of the paper produced was increased as a result of therelatively high intrinsic strength provided by the network region. Thesoftness of the paper produced was increased as a result of theprovision of the plurality of low density domes across the surface ofthe paper. The absolute quantity of fluid the paper would hold (one ofthe key factors in determining the absorbency of the paper) wasincreased due to the fact that the overall density of the paper wasreduced.

Although the aforementioned improved process worked quite well, it hasbeen found that when the deflection member of the above-describedprocess passed over vacuum dewatering equipment used in the papermakingprocess, certain undesirable events occurred. Of most concern was thefact that a large number of partially dewatered fibers in the paper webwould pass completely through the deflection member. This would lead tothe undesirable result of clogging the vacuum dewatering machinery withthe more mobile paper fibers. Another undesirable occurrence was thetendency of these mobile paper fibers to accumulate on the dewateringmachinery to the extent of producing clumps of fibers on the machinery.This accumulation of fibers would cause the previous papermaking beltswhich had smooth backsides to wrinkle and develop folds, particularlylongitudinal folds, after they repeatedly traveled over the dewateringmachinery during the papermaking process, which in turn would not onlyresult in severe problems with the moisture and physical propertyprofiles of the paper produced, but would result in the eventual failureof the papermaking belt.

The significance of the difficulties experienced with these prior beltswas increased by the relatively high cost of the belts. In most cases,manufacturing the foraminous woven element which was incorporated intothese belts required (and still requires) expensive textile processingoperations, including the use of large and costly looms. Also,substantial quantities of relatively expensive filaments areincorporated into these woven elements. The cost of the belts is furtherincreased when high heat resistant filaments properties are employed,which is generally necessary for belts which pass through a dryingoperation.

In addition to the cost of the belt itself, the failure of a papermakingbelt will also have serious implications on the efficiency of thepapermaking process. A high frequency of paper machine belt failures cansubstantially affect the economies of a paper manufacturing business dueto the loss of the use of the expensive papermaking machinery (that is,the machine "downtime") during the time a replacement belt is beingfitted on the papermaking machine.

At the time the papermaking process described in U.S. Pat. No 4,529,480was developed it was believed that the network formed in the lowersurface of the resinous framework (the machine-contacting surface) hadto be essentially planar in order to achieve the desired suddenness ofapplication of vacuum pressure needed to deflect and rearrange thefibers into the deflection conduits to form the dome regions in theimproved paper.

While not wishing to be bound by any theory, it is now believed that theproblems which developed when using the prior smooth backsidedpapermaking belts may have been at least partially the result of theextremely sudden application of vacuum pressure to the paper web when itpassed over the vacuum dewatering machinery. It is believed that theprior smooth backsided papermaking belts would actually temporarilycreate a seal over the vacuum source. Then, when the open channels (thedeflection conduits) of the papermaking belt of the prior type wereencountered, the vacuum pressure would be applied to the water laden,highly mobile fibers in the fibrous web situated on top of the resinframework in an extremely sudden fashion. This sudden application ofvacuum pressure is believed to have caused the sudden deflection of themobile fibers which was sufficient to allow them to pass completelythrough the papermaking belt. It is also believed that this suddenapplication of vacuum pressure and migration of fibers would account forpin-sized holes in the dome regions of the finished paper, which insome, but not all cases, are undesirable.

Another theory for the excessive accumulation of paper fibers on thesurfaces of the vacuum dewatering equipment is that the prior smoothbacksided papermaking belts did not have adequate surface texture ontheir backsides. It is believed that a certain amount of surface textureis necessary to enable such resin-coated belts to remove the paperfibers which accumulate on the vacuum dewatering equipment by theabrasive action of such a belt traveling over the vacuum dewateringequipment.

As a result, a need exists for an improved papermaking process whichwill not be plagued by the undesirable buildup of these mobilepapermaking fibers on the vacuum dewatering machinery employed in theprocess. A need, therefore, also exists for an improved papermaking beltand a method of making the same which will eliminate the foregoingproblems caused by utilizing a papermaking belt made by the priorprocesses.

Therefore, it is an object of the present invention to provide animproved papermaking process in which the migration of theaforementioned mobile paper fibers is substantially reduced, oreliminated.

It is also an object of the present invention to provide a papermakingbelt which will substantially reduce the previous problem of the buildupof paper fibers on the vacuum dewatering machinery which was associatedwith the prior resin coated papermaking belts.

It is another object of the present invention to reduce the folding andsubsequent failures of the papermaking belts due to the accumulation ofpaper fibers on the surface of the vacuum dewatering equipment employedin the papermaking process.

It is also an object of the present invention to develop a papermakingprocess which will result in the elimination of the pin-sized holes inthe dome regions of the finished paper web (unless such holes are adesirable characteristic for the particular paper being produced).

It is also an object of the present invention to provide a papermakingbelt which has passageways that provide surface texture irregularitieson the backside of the belt and a method of making this belt in whichthese passageways can be imparted to the belt without sacrificing thestrength of the entire papermaking belt.

It is a further object of the present invention to provide a papermakingbelt, which when employed in the papermaking process of the presentinvention will have a longer life than prior papermaking belts, and amethod of making this papermaking belt which is cost effective.

These and other objects of the present invention will be more readilyapparent when considered in reference to the following description andwhen taken in conjunction with the accompanying drawings.

SUMMARY OF THE INVENTION

The backside textured papermaking belt of the present invention isgenerally comprised of two primary elements: a framework and areinforcing structure. When the papermaking belt of the presentinvention is in its preferred form, it is an endless belt which has apaper-contacting side and a textured backside, opposite thepaper-contacting side, which contacts the machinery employed in thepapermaking process. The framework is preferably a cured polymericphotosensitive resinous framework which has a first surface whichdefines the paper-contacting side of the belt, a second surface oppositethe first surface, and conduits extending between the first and secondsurfaces. The first surface of the framework has a paper side networkformed therein which surrounds and defines the openings of the conduits.The second surface of the framework has a backside network withpassageways therein which are distinct from the conduits. Thepassageways provide surface texture irregularities in the backsidenetwork of the second surface. The reinforcing structure is positionedbetween the first surface of the framework and at least a portion of thesecond surface of the framework and serves to strengthen the framework.The reinforcing structure has a paper-facing side and a machine-facingside opposite the paper-facing side. The reinforcing structure also hasinterstices and a reinforcing component comprised of a plurality ofstructural components. A first portion of the reinforcing component hasa first opacity, and a second portion of the reinforcing component has asecond opacity which is less than the first opacity. The first opacityis sufficient to substantially prevent curing of the photosensitiveresinous material which comprises the framework when the photosensitiveresinous material is in its uncured state and the first portion of thereinforcing component is positioned between the photosensitive resinousmaterial and an actinic light source. The second opacity is sufficientto permit curing of the photosensitive resinous material. In addition,the first portion defines a first projected area. The position of thepassageways in the backside network of the framework relative to thereinforcing structure is such that the passageways are positionedpredominately within the first projected area.

The method of making the papermaking belt of the present inventioncomprises the steps of:

(a) providing a forming unit having a working surface;

(b) providing a reinforcing structure having a paper-facing side, amachine-facing side opposite the paper-facing side, interstices and areinforcing component comprised of a plurality of structural components,a first portion of the reinforcing component having a first opacity anda second portion of the reinforcing component having a second opacityless than the first opacity, the first opacity being sufficient tosubstantially prevent curing of the photosensitive resinous materialwhen the photosensitive resinous material is in its uncured state andthe first portion is positioned between the photosensitive resinousmaterial and an actinic light source, and the second opacity beingsufficient to permit curing of the photosensitive resinous material, thefirst portion defining a first projected area;

(c) bringing at least a portion of the machine-facing side of thereinforcing structure into contact with the working surface of theforming unit;

(d) applying a coating of liquid photosensitive resin to at least oneside of the reinforcing structure so that the coating forms a firstsurface and a second surface, the coating being distributed so that atleast a portion of the second surface of the coating is positionedadjacent the working surface of the forming unit, and portions of thesecond surface of the coating are positioned between the first portionof the reinforcing component and the working surface of the formingunit, and the paper-facing side of the reinforcing structure ispositioned between the first and second surfaces of the coating, whereinthe portion of the coating positioned between the first surface and thepaper-facing side comprises a resinous overburden;

(e) controlling the thickness of the overburden to a preselected value;

(f) providing a mask having opaque and transparent regions, the opaqueregions together with the transparent regions defining a preselectedpattern in the mask;

(g) positioning the mask between the coating of liquid photosensitiveresin and an actinic light source so that the mask is in contactingrelation with the first surface of the coating, the opaque regions ofthe mask shielding a portion of the coating from the light rays of thelight source and the transparent regions leaving other portions of thecoating unshielded;

(h) curing the unshielded portions of liquid photosensitive resincoating and those portions of the coating that the second portion of thereinforcing structure permits the curing of, and leaving the shieldedportions and those portions of the coating positioned between the firstportion of the reinforcing structure and the working surface of theforming unit uncured by exposing the coating of liquid photosensitiveresin to light having an activating wavelength from the light sourcethrough the mask and through the reinforcing structure to form apartially-formed composite belt; and

(i) removing substantially all uncured liquid photosensitive resin fromthe partially-formed composite belt to leave a hardened resin frameworkwhich has a plurality of conduits in those regions which were shieldedfrom the light rays by the opaque regions of the mask and passagewaysthat provide surface texture irregularities in the backside network ofthe framework which correspond to those portions of the second surfaceof the coating which were prevented from curing by the first portion ofthe reinforcing structure.

The process for making a strong, soft, absorbent paper web of thepresent invention comprises the steps of:

(a) providing an aqueous dispersion of papermaking fibers;

(b) forming an embryonic web of papermaking fibers from the dispersionon a foraminous surface;

(c) contacting the embryonic web with the paper-contacting side of thepapermaking belt of the present invention;

(d) traveling the papermaking belt and embryonic web over a vacuumsource and applying a fluid pressure differential to the embryonic webwith the vacuum source such that the fluid pressure differential isapplied from the backside of the papermaking belt through the conduitsof the papermaking belt to deflect at least a portion of the papermakingfibers in the embryonic web into the conduits of the papermaking belt,and to remove water from the embryonic web through the conduits, andrearrange the papermaking fibers in the embryonic web to form anintermediate web from the papermaking fibers under such conditions thatthe deflecting is initiated no later than the initiation of the waterremoval from the embryonic web;

(e) impressing the paper side network into the intermediate web byinterposing the intermediate web between the papermaking belt and animpression surface to form an imprinted web of papermaking fibers; and,

(f) drying the imprinted web,

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic representation of one embodiment of a continuouspapermaking machine useful in carrying out the process of thisinvention.

FIG. 1A is a simplified schematic representation of a cross-sectionwhich shows the partially-formed embryonic web of papermaking fibersprior to its deflection into a conduit of the papermaking belt of thepresent invention,

FIG. 1B is a simplified representation in cross-section of the portionof the embryonic web shown in FIG. 1A after the fibers of the embryonicweb have been deflected into one of the conduits of the papermakingbelt.

FIG. 2 is a plan view of a portion of the preferred embodiment of theimproved papermaking belt of the present invention.

FIG. 3 is an enlarged cross-sectional view of the portion of thepapermaking belt shown in FIG. 2 as taken along line 3--3.

FIG. 4 is an enlarged cross-sectional view of the portion of thepapermaking belt shown in FIG. 2 as taken along line 4--4.

FIG. 5 is a plan view of a portion of an alternative embodiment of thepapermaking belt of the present invention which has a monolayerreinforcing structure.

FIG. 5A is a cross-sectional view of the portion of the papermaking beltshown in FIG. 5 as taken along line 5A--5A.

FIG. 5B is a cross-sectional view of the portion of the papermaking beltshown in FIG. 5 as taken along line 5B--5B.

FIG. 6 is an enlarged plan view of a preferred woven multilayerreinforcing structure which can be used in the papermaking belt of thepresent invention.

FIG. 7 is an extended sectional view of the reinforcing structure shownin FIG. 6, taken along line 7--7 of FIG. 6.

FIG. 8 is an extended sectional view of the reinforcing structure ofFIG. 6 taken along line 8--8 of FIG. 6.

FIG. 9 is an extended sectional view of the reinforcing structure ofFIG. 6 taken along line 9--9 of FIG. 6.

FIG. 10 is an extended sectional view of the reinforcing structure ofFIG. 6 taken along line 10--10 of FIG. 6.

FIG. 11 is an extended sectional view of the reinforcing structure ofFIG. 6 taken along line 11--11 of FIG. 6.

FIG. 11A is a sectional view, similar to FIG. 8 but also showing aportion of the surrounding framework, which illustrates a variation ofone type of woven reinforcing structure which can be used in the presentinvention, in which the bottom warp yarns are opaque.

FIG. 11B is a sectional view, similar to FIG. 11A, which illustratesanother variation of one type of woven reinforcing structure in whichevery alternate bottom warp yarn is opaque.

FIG. 11C is a plan view, similar to FIG. 6, which illustrates anothervariation of one type of reinforcing structure which can be used in thepresent invention, in which a pattern is printed on the surface ofreinforcing structure with an opaque substance.

FIG. 12 is a plan view of a portion of the reinforcing structure shownwith part of the surrounding framework in place around the reinforcingstructure.

FIG. 12A is an end view of the portion of the reinforcing structure ofFIG. 12 which illustrates the position of some passageways and surfacetexture irregularities relative to several of the projected areas of thereinforcing structure.

FIG. 13 is a plan view of the reinforcing structure, similar to FIG. 6,which illustrates the projected reinforcing area of a portion of thereinforcing structure.

FIG. 14 is another plan view of the reinforcing structure, similar toFIG. 13, which illustrates some of the projected warp areas of thereinforcing structure.

FIG. 15 is an end view of the reinforcing structure, similar to FIG. 8,which illustrates the projected warp areas depicted in FIG. 14 fromanother angle.

FIG. 16 is another plan view of the reinforcing structure, similar toFIGS. 13 and 14 which illustrates some of the projected weft areas ofthe reinforcing structure.

FIG. 17 is an extended sectional view, similar to FIG. 7, whichillustrates the projected weft areas of the depicted in FIG. 16 fromanother angle.

FIG. 18A is a plan view of the reinforcing structure, similar to thepreceding plan views of the same, which illustrates some of theprojected knuckle areas of the reinforcing structure.

FIG. 18B is an extended sectional view of the reinforcing structure,similar to FIG. 7, which illustrates some of the projected knuckle areasof the reinforcing structure from another angle.

FIG. 18C is an end view of the reinforcing structure, similar to FIG. 8,which illustrates some of the other projected knuckle areas of thereinforcing structure from another angle.

FIG. 19 is an enlarged schematic representation of one preferred conduitopening geometry for the papermaking belt of the present invention.

FIGS. 19A and 19B are plan views which show, respectively, the projectedfirst surface knuckle area and the projected second surface knuckle areaof the framework of the papermaking belt shown in FIGS. 2 through 4.

FIG. 20 is an enlarged schematic representation of another preferredconduit opening geometry.

FIG. 21 is a greatly enlarged and exaggerated schematic sectional viewof a portion of the framework and reinforcing structure of a papermakingbelt which shows the details of the passageways and surface textureirregularities on the backside of the same.

FIGS. 22A, B, and C are simplified schematic representations ofdifferent types of the backside surface texturing which can be found ona papermaking belt.

FIG. 22D is a greatly enlarged view of a portion of a reinforcingcomponent, similar to the reinforcing component shown in FIGS. 22A-C,which shows some of the raised portions of the reinforcing component.

FIG. 23A is an enlarged schematic representation of the problems whichoccurred when a papermaking belt without the improvements disclosedherein encountered the vacuum dewatering equipment during thepapermaking process.

FIG. 23B is an enlarged schematic representation of the manner in whichthe papermaking belt of the present invention alleviates the problemsencountered previously.

FIG. 24 is a graphical representation which depicts the application ofvacuum pressure to a papermaking belt both with and without the backsidetexture disclosed herein.

FIG. 25 is a schematic representation of the basic apparatus for makingthe papermaking belt of the present invention.

FIG. 26 is an enlarged schematic representation of the post-cure unit ofthe apparatus shown in FIG. 25.

FIG. 27 is an enlarged schematic representation of a process for makingthe papermaking belt of the present invention by casting photosensitiveresin on a woven multilayer reinforcing structure which has opaqueyarns.

FIG. 28 is an enlarged schematic sectional view taken along line 28--28of FIG. 27 showing a portion of the casting surface and those portionsof the photosensitive resin which remain uncured to provide surfacetexture irregularities in the backside of the papermaking belt of thepresent invention.

FIG. 29 is an enlarged schematic sectional view of a portion of thecasting surface shown in FIG. 27, generally similar to FIG. 28, whichshows an alternative embodiment of the reinforcing structure shown inFIG. 28.

FIG. 30 is a schematic plan view of a portion of the testing apparatuswhich is used to measure air leakage across the backside of thepapermaking belt of the present invention.

FIG. 31 is a schematic side view of the testing apparatus shown in FIG.31.

FIG. 32 is a graphical representation of the calibration of the flowmeter used in the apparatus shown in preceding two figures.

FIG. 33A is a plan view photograph, enlarged about 25 times actual size,of the top side of a papermaking belt which does not contain theimprovements disclosed herein.

FIG. 33B is a plan view photograph, enlarged about 25 times actual size,of the backside of a papermaking belt which does not contain theimprovements disclosed herein.

FIG. 34A is a photograph, enlarged about 25 times, of the top side of apapermaking belt made in accordance with the method of the presentinvention. The photograph was taken at an angle of approximately 35degrees relative to an imaginary line drawn normal to the surface of thetop side.

FIG. 34B is a photograph, enlarged about 25 times, of the backside ofthe papermaking belt shown in FIG. 34A. The photograph was taken at anangle of approximately 35 degrees relative to an imaginary line drawnnormal to the surface of the backside. FIG. 34C is a cross-machinedirection view photograph, enlarged about 25 times, of the papermakingbelt shown in FIGS. 34A and 34B.

DETAILED DESCRIPTION OF THE INVENTION

The specification contains the following, in order: a detaileddescription of the papermaking belt of the present invention; the methodof making this papermaking belt; and a detailed description of theprocess for making paper according to the present invention.

1. The Papermaking Belt

In the representative papermaking machine illustrated in FIG. 1, thepapermaking belt of the present invention takes the form of an endlessbelt, papermaking belt 10. In FIG. 1, the papermaking belt 10 carries apaper web (or "fiber web") in various stages of its formation andtravels in the direction indicated by directional arrow B around thepapermaking belt return rolls 19a and 19b, impression nip roll 20,papermaking belt return rolls 19c, 19d, 19e and 19f, and emulsiondistributing roll 21. The loop the papermaking belt 10 travels aroundincludes a means for applying a fluid pressure differential to the paperweb, such as vacuum pickup shoe 24a and multislot vacuum box 24. In FIG.1, the papermaking belt also travels around a predryer such asblow-through dryer 26, and passes between a nip formed by the impressionnip roll 20 and a Yankee dryer drum 28.

Although the preferred embodiment of the present invention is in theform of an endless belt, the present invention can be incorporated intonumerous other forms which include, for instance, stationary plates foruse in making handsheets or rotating drums for use with other types ofcontinuous processes. Regardless of the physical form which thepapermaking belt 10 takes, it generally has certain physicalcharacteristics.

The overall characteristics of the papermaking belt 10 of the presentinvention are shown in FIGS. 2-4. The papermaking belt (or simply the"belt") 10 of the present invention is generally comprised of twoprimary elements: a framework 32 (preferably, a hardened polymericphotosensitive resin framework) and a reinforcing structure 33. When thepapermaking belt 10 is an endless belt, it generally has two opposedsurfaces which are referred to herein as the paper-contacting side 11and the textured backside, or simply, the backside 12. The backside 12of the belt 10 contacts the machinery employed in the papermakingoperation, such as vacuum pickup shoe 24a and multislot vacuum box 24.The framework 32 has a first surface 34, a second surface 35 oppositethe first surface 34, and conduits 36 extending between the firstsurface 34 and the second surface 35. The first surface 34 of theframework 32 contacts the fiber webs to be dewatered, and defines thepaper-contacting side 11 of the belt. The conduits 36 extending betweenthe first surface 34 and the second surface 35 channel water from thefiber webs which rest on the first surface 34 to the second surface 35and provide areas into which the fibers of the fiber web can bedeflected and rearranged. FIG. 2 shows that the network 32a comprisesthe solid portion of the framework 32 which surrounds the conduits 36defines a net-like pattern. As shown in FIG. 2, the openings 42 of theconduits 36 are arranged in a preselected pattern in the network 32a.FIG. 2 shows that the first surface 34 of the framework 32 has a paperside network 34a formed therein which surrounds and defines the openings42 of the conduits 36 in the first surface 34 of the framework 32. Aswill be subsequently shown in FIG. 34B, the second surface 35 of theframework 32 has a backside network 35a which surrounds and defines theopenings 43 of the conduits 36 in the second surface 35 of the framework32. FIGS. 3 and 4 show that the reinforcing structure 33 of thepapermaking belt 10 of the present invention, in general, is at leastpartially surrounded by and enveloped (or embedded, or encased) in theframework 32. More specifically, the reinforcing structure 33 ispositioned between the first surface 34 of the framework 32 and at leasta portion of the second surface 35 of the framework 32. FIGS. 3 and 4also show that the reinforcing structure 33 has a paper-facing side 51and a machine-facing side 52, opposite the paper-facing side 51. Asshown in FIG. 2, the reinforcing structure 33 has interstices 39 and areinforcing component 40. The reinforcing component 40 comprises theportions of the reinforcing structure exclusive of the interstices 39(that is, the solid portion of the reinforcing structure 33). Thereinforcing component 40 is generally comprised of a plurality ofstructural components 40a. The reinforcing structure 33 has a projectedopen area defined by the projection of the areas defined by theinterstices 39, and a projected reinforcing area defined by theprojection of the reinforcing component 40. FIGS. 3 and 4 show that thesecond surface 35 of the framework 32 has a backside network 35a with aplurality of passageways 37 that provide surface texture irregularities38 in the backside network 35a of the framework 32. The passageways 37are distinct form the conduits 36 which extend between the first surface34 and second surface 35 of the framework 32. The passageways 37 allowair to enter between the backside surface 12 of the papermaking belt 10and the surfaces of the vacuum dewatering equipment employed in thepapermaking process (such as vacuum pickup shoe 24a and vacuum box 24)when a vacuum is applied by the dewatering equipment to the backside 12of the belt to deflect the fibers into the conduits 36 of the belt 10.The surface texture irregularities 38 provide an uneven surface forcontacting the machinery employed in the papermaking operation.

The paper-contacting side 11 of the belt 10 shown in FIGS. 1-4 is thesurface of the papermaking belt 10 which contacts the paper web which isto be dewatered and rearranged into the finished product. As shown inFIG. 1, the side of the belt 10 referred to as the paper-contacting side11 is referred to as such even though it only carries a paper web for aportion of each revolution in the papermaking machine. The side of thebelt 10 referred to as the paper-contacting side 11 is also consistentlyreferred to as such even though during a portion of each revolution(such as adjacent papermaking belt return roll 19d), it may briefly comein contact with the machinery employed in the papermaking process. Thepaper-contacting side 11 of the belt 10 may also be referred to as the"top surface" or the "embryonic web-contacting surface" of the belt 10.It is to be understood that although the paper-contacting side 11 of thebelt 10 may be referred to as the top surface, the orientation of thepaper-contacting side 11 may be such that it is facing downwardly on thereturn path in a papermaking machine when the belt 10 is in theconfiguration of an endless belt. As shown in FIGS. 2-4, thepaper-contacting side 11 of the belt 10 is generally formed entirely bythe first surface 34 of the framework 32.

As shown in FIG. 1, the opposed surface of the belt 10, the backside 12,is the surface which travels over and is generally in contact with thepapermaking machinery employed in the papermaking process, such as thepapermaking belt return rolls 19a-19c and 19e and 19f and the vacuumpickup shoe 24a and vacuum box 24, as well as other vacuum dewateringequipment not illustrated in the drawings. FIG. 1 shows that the side ofthe belt 10 referred to as the backside 12 is referred to as such eventhough it may occasionally face away from the machinery employed in thepapermaking process (such as adjacent papermaking belt return roll 19d).The backside 12, however, can be distinguished from the paper-contactingside 11 because the backside 12 never contacts a paper web during thepapermaking process. The backside 12 of the papermaking belt 10 of thepresent invention may also be referred to herein as the "bottom surface"of the belt. It may also be referred to as the "wear surface" of thebelt because it is the surface of the belt which is subjected to theabrasive action of being repeatedly traveled over the papermakingmachinery during the papermaking process. It is to be understood thatalthough the backside 12 of the belt 10 may be referred to as the bottomsurface, the orientation of the backside 12 may be such that it isfacing upward on the return path in a papermaking machine when the belt10 is in the configuration of an endless belt. As a general matter, thebackside 12 of a belt which comprises a framework and a reinforcingstructure may be formed entirely by the backside network 35a of theframework 32, although such an embodiment may not occur often in thepapermaking belt 10 of the present invention. Alternatively, thebackside 12 may be formed entirely by the machine-facing side 52 of thereinforcing structure 33; or, it may be formed partially by the backsidenetwork 35a of the framework 32 and partially by the machine-facing side52 of the reinforcing structure 33. It is this bottom surface orbackside 12 and the methods of creating passageways and surface textureirregularities in the same which are of primary importance in thisinvention.

The reinforcing structure 33, one of the primary elements of thepapermaking belt 10 of the present invention, is shown in FIGS. 2-4. Thereinforcing structure 33 strengthens the resin framework 32 and hassuitable projected open area to allow the vacuum dewatering machineryemployed in the papermaking process to adequately perform its functionof removing water from partially-formed webs of paper, and to permitwater removed from the paper web to pass through the papermaking belt10. The reinforcing structure 33 can take any number of different forms.The reinforcing structure 33 can comprise a woven element (alsosometimes referred to herein as a woven "fabric"), a nonwoven element, ascreen, a net (for instance, thermoplastic netting), a scrim, or a bandor plate (made of metal or plastic or other suitable material) with aplurality of holes punched or drilled in it provided the reinforcingstructure 33 adequately reinforces the framework 32 and has sufficientprojected open area for the purposes specified above. Preferably, thereinforcing structure 33 comprises a woven element (or moreparticularly, a foraminous woven element) such as that shown in FIGS.2-4.

Generally, as shown in FIGS. 2-4, the reinforcing structure 33 comprisesa reinforcing component 40 and a plurality of interstices (or "fineforamina") 39. The reinforcing component 40 is the portion of thereinforcing structure 33 exclusive of the interstices 39. In otherwords, the reinforcing component 40 is the solid portion of thereinforcing structure 33. The reinforcing component 40 is comprised ofone or more structural components 40a. As used herein, the term"structural components" refers to the individual structural elementsthat comprise the reinforcing structure 33.

The interstices 39 allow fluids (such as water removed from the paperweb) to pass through the belt 10. The interstices 39 form one of thegroups of openings in the papermaking belt 10. FIG. 2 shows that theinterstices 39 may form a pattern in the reinforcing structure 33. Thepattern formed by the interstices 39, however, is to be contrasted withthe preselected pattern formed by the conduit openings, such as firstconduit openings 42. FIG. 2 shows that typically, each interstice 39 isonly a fraction of the size of a conduit opening 42, but the alternaterelationship is possible.

As shown in FIGS. 3 and 4, the reinforcing structure 33 has two sides.These are the paper-facing side (or the "paper support side"), generallydesignated 51, which faces the fiber webs to be dewatered, and themachine-facing side (or "roller contact side") generally designated 52,opposite the paper-facing side, which faces the machinery employed inthe papermaking operation. The sides of the reinforcing structure 33referred to as the paper-facing side 51 and the machine-facing side 52are referred to as such even though there may be brief portions of eachrevolution of the papermaking belt 10 when they face in the oppositedirection. In addition, the respective sides of the reinforcingstructure 33 are consistently referred to by these names even prior tothe incorporation of the reinforcing structure 33 into the papermakingbelt 10 of the present invention and the installation of the belt 10 ina papermaking machine. Thus, the side of the reinforcing structure 33referred to as the machine-facing side 52 in the method of making thepapermaking belt 10 of the present invention will be that side whichgenerally faces the papermaking machinery when the finished belt isinstalled in a papermaking machine. The paper-facing side 51 will alwaysbe opposite the machine-facing side 52. As shown in FIGS. 3 and 4, thereinforcing structure 33 is positioned between the first surface 34 ofthe framework 32 and at least a portion of the second surface 35 of theframework 32.

FIGS. 2-4 show that when the reinforcing structure 33 comprises a wovenelement, the individual yarns which are woven together to form the wovenelement comprise the structural components 40a of the reinforcingstructure 33. If the reinforcing structure 33 comprised a nonwovenelement, the individual fibers forming the nonwoven element wouldcomprise the structural components 40a. In both cases, there will be aplurality of structural components such that all of these structuralcomponents 40a will together comprise the reinforcing component 40. If,on the other hand, the reinforcing structure 33 is a plate with aplurality of holes punched in it, there will be only one structuralcomponent 40a (the plate), and this will comprise the reinforcingcomponent 40.

The structural components 40a of a woven reinforcing structure compriseyarns, strands, filaments, or threads. It is to be understood that theterms yarns, strands, filaments, and threads are synonymous when used todescribe the structural components 40a of a woven reinforcing structure.It is also to be understood that the above terms (yarns, strands, etc.)could comprise not only monofilament elements, but also multifilamentelements.

When the reinforcing structure 33 comprises a woven element, as shown inFIGS. 2-4, some of the individual structural components 40a comprisemachine-direction warp yarns, generally designated 53, and some comprisecross-machine direction weft yarns, generally designated 54. As usedherein, the terms "machine-direction warp", "warp", and "load-bearingwarp" are synonymous and refer to yarns which are generally oriented inthe machine direction when the papermaking belt 10 of the presentinvention is installed in a papermaking machine. As used herein, theterms "cross-machine direction weft", "weft", "shute", and "warpbalancing weft" are synonymous and refer to yarns which are generallyoriented in the cross-machine direction when the papermaking belt 10 ofthe present invention is installed in a papermaking machine.

In papermaking, the term "machine direction" (MD) refers to thatdirection which is parallel to the flow of the paper web through theequipment. The "cross-machine direction" (CD) is perpendicular to themachine direction. These directions are indicated by arrows in FIG. 2and in several of the figures which follow.

The definitions of warp yarns and weft yarns used herein may sometimesdiffer from the definitions of those terms when describing theorientation of the yarns of a woven fabric when it is being woven in aloom. In the weaving art, whether a yarn is referred to as a warp or aweft depends in part upon whether the fabric is an endless woven fabricthat does not have to be seamed into a loop to form an endless belt, orwhether it is a flat woven fabric which must be seamed into a loop toform an endless belt. For an endless woven fabric that need not beseamed into a loop, the threads which are referred to as warps in theloom will extend crosswise in a papermaking machine. On the other hand,if a fabric is woven flat, and then seamed into a loop, the threadswhich are referred to as warp threads in the loom will extend in themachine direction in a papermaking machine. As used herein, the terms"warp yarns" and "weft yarns" refer to the orientation of the yarns whenthe fabric is in place on a papermaking machine, rather than while it isbeing woven in a loom. Thus, "warp yarns" means machine-direction warpyarns, and "weft yarns" means cross-machine direction weft yarns whenthe papermaking belt of the present invention is installed on apapermaking machine.

FIGS. 2-4 also show that in a woven reinforcing structure 33, some ofthe yarns will cross to form knuckles 105 in the fabric. As used hereina "knuckle" is either a portion of a weft yarn that passes over a warpyarn or a portion of a warp yarn that passes over a weft yarn which liesin the plane of one of the surfaces (that is, either the paper-facingside 51, or the machine-facing side 52) of the reinforcing structure 33.Knuckles which lie in the paper-facing side 51 of the reinforcingstructure 33 (or "paper side knuckles") are designated 105₁. Knuckleswhich lie in the machine-facing side 52 (or "backside knuckles") aredesignated 105₂. These knuckles 105 may be further classified herein andreferred to as either "warp knuckles", or "weft knuckles".

As used herein, the term "warp knuckles" will refer to the knucklesformed by a portion of a warp yarn that passes over a weft yarn. Severalsuch warp knuckles are designated 105a in the alternative embodiment ofthe papermaking belt 10 of the present invention shown in FIG. 5 (whichincludes a monolayer reinforcing structure 33). As shown incross-section in FIG. 5B, the warp knuckles 105a can lie either in thepaper-facing side 51 or in the machine-facing side 52 of the reinforcingstructure 33. Warp knuckles which lie in the paper-facing side 51 of thereinforcing structure 33 are designated 105a₁, and warp knuckles whichlie in the machine-facing side 52 are designated 105a₂.

The knuckles formed by a portion of a weft yarn that passes over a warpyarn are referred to herein as "weft knuckles". Several such weftknuckles are shown as 105b in FIGS. 2 and 3. FIG. 3 shows that the weftknuckles, like the warp knuckles, can either lie in the paper-facingside 51 of the reinforcing structure 33, such as weft knuckle 105b₁, orthey can lie in the machine-facing side 52 of the reinforcing structure33, such as weft knuckle 105b₂.

Many types of woven elements are suitable for use as a reinforcingstructure 33 in the papermaking belt 10 of the present invention.Suitable woven elements include foraminous monolayer woven elements(having a single set of strands running in each direction and aplurality of openings therebetween) such as the reinforcing structure 33shown in FIGS. 5, 5A, and 5B, multilayer woven elements (woven fabricshaving more than one set of strands running in at least one direction),and fabrics with several layers each of which comprises interwovenstrands.

Multilayer woven fabrics are preferred as reinforcing structures becausethey can extend the useful life of the composite papermaking belt. Asused herein, the term "composite papermaking belt" refers to a beltwhich is comprised of a framework and a reinforcing structure. Thepapermaking belt 10 comes under considerable stress in the machinedirection due to the repeated travel of the belt 10 over the papermakingmachinery in the machine direction and also due to the heat transferredto the belt by the drying mechanisms employed in the papermakingprocess. Such heat and stress give the papermaking belt a tendency tostretch. If the papermaking belt 10 should stretch out of shape, itsability to serve its intended function of carrying a paper web throughthe papermaking process becomes diminished to the point of uselessness.

To be suitable for use as a reinforcing structure in the papermakingbelt of the present invention, a multilayer woven element preferably hassome type of structure which provides for reinforcement of its machinedirection yarns 53 in order to reduce the aforementioned stretchingproblem. In other words, the multilayer fabric must have increasedfabric stability in the machine-direction. The arrangement of the warpyarns 53 should be such that any additional reinforcement of the warpyarns does not reduce the projected open area of the reinforcingstructure 33.

As used herein, the term "projected area" means the area formed byprojecting the points which define the element in issue into a plane.More particularly, it is to be understood that these points will beprojected in a direction which will be referred to as the "z-direction".The projected open area of the reinforcing structure is shown as A₀ inFIG. 12 of the accompanying drawings. As used herein, the term"projected open area" refers to the projected area defined by theprojection in the z-direction of all the areas defined by theinterstices 39 of the reinforcing structure 33. In other words, theprojected open area A₀ of the reinforcing structure 33 is that area seenwhen the reinforcing structure 33 is viewed from a directionperpendicular to either side of the reinforcing structure 33 through theinterstices 39 which provide direct lines of sight through the fabric.

Throughout this description, references will be made to the x, y, and zdirections. As used herein, the x, y, and z directions are orientationsrelating to the papermaking belt of the present invention (or portionsthereof) in a Cartesian coordinate system. In the Cartesian coordinatesystem described herein, the backside 12 of the belt lies in the planeformed by the x and y axes. The x axis is the cross-machine direction,the y axis is the machine direction, and the z axis is perpendicular tothe plane defined by the x and y axes. As used herein, the "z-direction"refers to those orientations which run parallel to the z axis andperpendicular to the x and y axes. These directions are best shown inFIGS. 2-4.

The projected open area of the reinforcing structure 33 shouldpreferably be such that the reinforcing structure 33 is highly permeable(to fluids such as air and water). By "highly permeable" it is meantthat the reinforcing structure 33 should have an air permeability in therange of about 800 cfm to about 1,400 cfm per ft.² of its surface at apressure differential of 100 pascals. The air permeability of thereinforcing structure 33 is of primary importance because it contributeswith the framework to establish an air permeability for the compositebelt. The composite belt should have an air permeability in the range ofabout 300 cfm to about 600 cfm. The preferred air permeability for thecomposite belt is about 500 cfm. In order for both the reinforcingstructure 33 and composite belt to be sufficiently permeable, it ispreferable that the projected open area A₀ of the reinforcing structure33 not be reduced below about 30%, and most preferably that theprojected open area not be reduced below about 40% to about 50%.

As shown in FIGS. 2-4, a preferred reinforcing structure 33 is amultilayer woven element that has a single layer yarn system with yarnswhich extend in a first direction and a multiple layer yarn system withyarns which extend in a second direction which is normal to the firstdirection. In the preferred reinforcing structure 33 shown in FIGS. 2-4,the first direction is the cross-machine direction. The single layer ofyarns which extend in the first direction comprise the weft yarns 54. Inthe reinforcing structure 33 shown in FIGS. 2-4, the multiple layer yarnsystem extends in the machine direction (that is, the direction thefabric travels on a papermaking machine). The multiple layer yarn systemcomprises a first warp layer C, and a second warp layer D. Each of thewarp layers C and D comprises a plurality of warp yarns 53. Although themost preferred fabrics for use as a reinforcing structure have multiplemachine direction warp yarns, the present invention can also bepracticed using a fabric which has multiple strands in the cross-machinedirection. Fabrics having multiple machine direction warp yarns arepreferred, however, because the additional strands run in the directionwhich is generally subject to the greatest stresses.

As shown in FIG. 3, the preferred multilayer reinforcing structure 33has warp yarns 53 which are vertically stacked directly on top of oneanother. The vertically-stacked warp yarns 53 provide increasedstability for the composite belt 10 in the machine or process direction.The stacked arrangement of the warp yarns also provides suitableprojected open area so the belt 10 can be used in a variety of types ofpapermaking processes, including blow-through drying papermakingprocesses. The weft yarns 54 are preferably arranged in such a mannerthat they maintain and stabilize the warp yarns 53 in avertically-stacked arrangement. The weft yarns 54 may also be verticallystacked, or they may be in some other relationship. Numerous variationsof such arrangements are possible.

FIGS. 6 through 11 show the details of the weave pattern of theparticular preferred multilayer reinforcing structure 33 shown in FIGS.2-4. As used herein, the term "weave pattern" means the technical designof a weave. The multilayer fabric is shown in FIGS. 6 through 11 withoutthe surrounding framework for clarity of illustration. Although the samefabric is shown in FIGS. 2-4 as a composite element in a papermakingbelt (that is, as a reinforcing structure for reinforcing the framework32 of the papermaking belt 10 of the present invention), the fabricshown is also suitable for use by itself as a papermaking belt withoutsuch a framework. However, the multilayer fabric described herein ispreferably used in conjunction with a framework of some type.

Generally, as shown in FIGS. 6 through 11, the first warp layer C ofwarp yarns 53 extend in the machine direction on the paper-facing side51 of the fabric. The individual warp yarns in the first warp layer Care numbered repeatedly across the fabric as 53a, 53b, 53c, and 53d. Thesecond layer D of warp yarns 53 extend in the machine direction on themachine-facing side 52 of the fabric. The individual warp yarns in thesecond warp layer D are numbered repeatedly across the fabric as 53e,53f, 53g, and 53h. As best shown in FIGS. 8-11, the individual yarns inthe first warp layer C and the second warp layer D define stacked warpyarn pairs E, F, G, and H. The individual yarns which define the stackedwarp yarn pairs E, F, G, and H are arranged in a generallyvertically-stacked superposed position one over the other. These stackedwarp yarn pairs, E, F, G, and H, are also repeatedly numbered across thefabric. FIGS. 8-11 show that the individual warp yarns 53a and 53edefine stacked warp yarn pair E; warp yarns 53b and 53f define stackedwarp yarn pair F; warp yarns 53c and 53g define stacked warp yarn pairG; and, warp yarns 53d and 53h define stacked warp pair H. As shown inFIG. 6 and in FIGS. 8-11, the adjacent stacked warp yarn pairs arespaced apart in the cross-machine direction to provide the desiredfabric open area.

As shown in FIG. 6, since the warp yarns 53 are stacked on top of oneanother, the effective density of the warps yarns 53 (or "threaddensity" of the warp yarns) is doubled without decreasing the open areaof the reinforcing structure 33. As used herein, the term "threaddensity" refers to a measurement which equals the product of the numberof threads per unit width of the fabric (which unit of width generallyused is an inch) and the thread diameter (which is also generallymeasured in inches). The term "thread density" can more particularly beexpressed for the warp yarns of a fabric (i.e., the warp thread density)or the weft yarns of a fabric (i.e., the weft thread density).

A weft yarn, such as weft yarn 54a in FIG. 8, 54b in FIG. 9, 54c in FIG.10, and 54d in FIG. 11 is interwoven with the warp yarns 53a-h in thefirst and second warp layers. The weft yarns bind the individual warpyarns in the first and second warp yarn layers in stacked pairs andprevent the warp yarns 53a-h from shifting laterally so as to reduce theopen area of the fabric. These weft yarns 54a, 54b, 54c, and 54d arealso numbered repeatedly across the fabric. The weft yarns 54 areinterwoven in a specific weave pattern (or more particularly, a "warpbalancing weave pattern") with the stacked pairs of the warp yarns. Theweft yarns 54 maintain the warp yarns stacked upon one another and ingeneral vertical alignment.

The particular weave pattern of the warp yarns 53 and the weft yarns 54in the fabric shown in FIGS. 6 through 11, is known as a four-shedrepeat pattern. As used herein, the term "shed" refers to the number ofunique configurations either a warp yarn or a weft yarn forms with thethreads with which it is interwoven before a repeat occurs (i.e., afour-shed pattern would be a pattern which repeats after every group offour threads).

The specific pattern of weaving the warp yarns 53 is shown best in FIGS.6 and 7. As shown in FIGS. 6 and 7, the first warp yarns of the firstwarp layer C (such as warp yarn 53b shown in FIG. 7) repeatedly passover three and under one of the picks of the weft yarns in the weavepattern. As used herein, the term "pick" refers to inserting a weft yarnbetween divided warp yarns. The second warp yarns of the second warplayer D (such as warp yarn 53f shown in FIG. 7) repeatedly pass over oneand under three of the picks of the weft yarns in the weave pattern.

The specific pattern of weaving the weft yarns 54 is shown best in FIGS.6 and 8-11. As shown in FIGS. 8-11, the warp yarns 53 are maintained invertically-stacked relationship by a weft system which consists of asingle network of weft yarns 54 woven between the stacked warp yarns.The weft yarns 54 are woven around the stacked warps in a repeatingpattern in which a weft yarn (such as weft yarn 54a in FIG. 8) firstpasses over the first stacked pair of warp yarns E, between the warpyarns of the second stacked pair F, under the third stacked pair G, andbetween the warp yarns of the fourth stacked pair H. In other words,each weft yarn 54 passes over and under every other pair of stacked warpyarns and between the warp yarns of the intermediate stacked pairsdisposed between every other stacked pair.

As shown in FIG. 6 and in FIGS. 8-11, the neighboring weft yarns arewoven around the warp yarns 53 in the same manner. However, as shown inFIG. 9, the adjacent weft yarns, such as weft yarn 54b, is displaced apair of warps from that of the first weft yarn. Thus, the adjacent orsecond weft yarn passes: between the warp yarns of the first stackedpair, over the second stacked pair of warp yarns, between the warp yarnsof the third stacked pair, and under the fourth stacked pair of warpyarns. As shown in FIGS. 10 and 11 respectively, the third weft yarn 54cis similarly displaced one pair of warp yarns from the second, and thefourth weft yarns 54d is displaced one pair of warp yarns from the third54c. This pattern repeats every fourth weft yarn. As shown in FIG. 6,this produces a weave pattern in which the cross-over points 55 formedby the weft yarns 54 are staggered in the weft direction across the warpyarns.

A variation of the preceding weave pattern can be achieved byinterchanging weft yarn 54c shown in FIG. 10 with weft yarn 54d shown inFIG. 11. This results in a broken, staggered pattern of cross-overpoints 55 of the weave in the weft direction. In this broken pattern,the first two cross-over points 55 are in a straight diagonal line. Thethird cross-over point 55, however, is shifted over a third warp yarn toa fourth warp yarn and the fourth cross-over point 55 shifted over athird warp yarn to a fourth warp yarn and then the cross-over point 55is shifted back in a diagonal to the third warp yarn. This weave patternalso maintains the warp yarns in stacked pairs in a suitableconfiguration. However, in this variation of the weave pattern, the twowarp yarns pass together between two adjacent picks. In the firstdescribed weave pattern, there are no two picks between which the warpyarns simultaneously pass, which provides a slightly better balance inthe weave pattern.

Various combinations of materials, cross-sectional dimensions, andcross-sectional shapes of yarns may be utilized in this preferredfabric. The yarn material, cross-sectional dimensions, and thecross-sectional shapes of the yarns will be determined by the particularapplication being made of the fabric.

While the specific materials of construction of the warp yarns and weftyarns can vary, the material comprising the yarns should be such thatthe yarns will be capable of reinforcing the resinous framework andsustaining stresses as well as repeated heating and cooling withoutexcessive stretching. Suitable materials from which the yarns can beconstructed include, polyester, polyamid, high heat resistant materialssuch as KELVAR or NOMEX brands, and any other materials which are knownfor use in papermaking fabrics. The preferred material for the yarns,however, is polyester. The material of construction of the yarns in thedifferent layers and yarn systems can vary with the yarns in one layeror yarn system being constructed of one material and the yarns of theother layers or yarn systems being constructed of a different material.Preferably, however, all of the yarns in the different layers and yarnsystems are constructed of essentially the same material.

Any convenient cross-sectional dimensions (or size) of the yarns can beused as long as the flow of air and water through the conduits 36 is notsignificantly hampered during the paper web processing and as long asthe integrity of the papermaking belt 10 as a whole is maintained. Yarnshaving the same cross-sectional dimensions can be used in all of thelayers or yarn systems, or the size of the yarns in the different layersand yarn systems can vary. For example, if yarns having a roundcross-sectional are used, the yarns of warp systems C and D may be ofone diameter, and the yarns of weft system may be of a larger or smallerdiameter. If larger diameter weft yarns are used, the weft yarns will bestiffer and place more crimp in the warp yarns. Other variations includethose in which the yarns of the warp system C and the weft system 54 areidentical, and the yarns of the warp system D are different. Likewise,the yarns of the warp system D and the yarns of the weft system may beidentical, and the yarns of the warp system C different. Alternatively,the yarns in each of the warp system C, warp system D, and the weftsystem can be different. For yarns having round cross-sections, apreferred range of yarn diameters is from about 0.10 mm to about 0.30mm. The most preferred diameters are about 0.22 mm for the warp yarns 53and about 0.28 mm for the weft yarns 54. Depending on the application,larger diameter yarns may also be used.

Yarns of any suitable cross-sectional shape can be used as long as theyarns do not interfere with the flow of fluids through the conduits 36during web processing and as long as the integrity of the papermakingbelt 10 as a whole is maintained. Suitable cross-sections include round,oval, square, and rectangular shapes. The cross-sectional shapes of theyarns in the different layers and yarn systems can also vary between thelayers and yarn systems. Preferably, however, both the warp yarns 53 andthe weft yarns 54 have round cross-sections.

In addition, regardless of whether the reinforcing structure 33 is themultilayer woven structure described above, or some other structure,such as a scrim or a plate with holes punched in it, a first portion P₀₁of the reinforcing component 40 which comprises the reinforcingstructure 33 has a first opacity O₁, and a second portion P₀₂ of thereinforcing component 40 has a second opacity O₂. The two opacities O₁and O₂ are related such that the second opacity O₂ is less (that is,relatively less opaque) than the first opacity O₁. o The first opacityO₁ should be sufficient to substantially prevent the curing of thephotosensitive resinous material which comprises the framework 32 whenthat photosensitive resinous material is in its uncured state and thefirst portion P₀₁ is positioned between the photosensitive resinousmaterial and an actinic light source. It should be understood that onlya portion of this photosensitive resinous material is positioned on theopposite side of the first portion P₀₁ with respect to the light source.The rest of the resinous material will be in other locations. Thepurpose of the first portion (or "the opaque portion") P₀₁ is to preventthe portion of the resinous material which is positioned on the otherside of the first portion P₀₁ from curing during the method of makingthe papermaking belt 10 of the present invention. This uncured resin canbe removed to leave passageways 37 that provide surface textureirregularities 38 in the backside network 35a on the backside 12 of thebelt 10.

The characteristics and the dimensions of the first portion P₀₁ shouldbe such that the passageways 37 and surface texture irregularities 38created by the removal of the uncured resin provide the desired amountof backside texture to the finished belt (as hereinafter described). Thefirst portion P₀₁ should generally be located near or on themachine-facing side 52 of the reinforcing structure 33. Such a locationwill ensure that the resin which is prevented from curing lies generallyalong the second surface 35 of the framework 32 of the belt, rather thanin the interior portion of the framework 32. As used herein, the"interior portion" is that portion of the framework 32 which liesbetween the first and second surfaces 34 and 35. If the first portionP₀₁ is not so located, an excessive amount of resin between the firstand second surfaces 34 and 35 of the framework 32 will remain uncured.This will greatly weaken the framework 32 and will also weaken the bondbetween the framework 32 and the reinforcing structure 33.

The first portion P₀₁ can be any portion of the reinforcing component 40provided that it prevents the resin from curing sufficiently to form thedesired passageways 37 and surface texture irregularities 38 in thebackside network 35a. Thus, the first portion P₀₁ can comprise a portionor portions of one or more of the structural components 40a. When thereinforcing structure 33 comprises a woven element, the first portionP₀₁ can, for example, be a portion or portions of a single yarn, aportion or portions of several yarns, an entire yarn, several entireyarns, or any combination of the same.

In one preferred embodiment of the present invention, the first portionP₀₁ comprises an entire warp yarn or yarns. It is generally preferablethat the warp yarns 53, rather than the weft yarns 54, comprise thefirst portion P₀₁. The reason for this preference is that in thepreferred woven reinforcing structures, the weaving pattern of the warpyarns 53 will cause them to be generally disposed closer to what willbecome the second surface 35 of the framework 32 than the weft yarns 54.Most preferably, the reinforcing structure 33 comprises the preferredmultilayer woven element having vertically-stacked warp yarns describedabove, and the first portion P₀₁ comprises at least some of the warpyarns in the second warp layer D. This preferred arrangement is shown inFIGS. 3 and 4. Since the first portion P₀₁ is described as comprising atleast some of the warp yarns 53 in the second warp layer D, the firstportion P₀₁ can, for instance, comprise every alternating warp yarn (asshown in FIG. 11B), or every warp yarn (as shown in FIGS. 3 and 4, andin FIG. 11A), every third warp yarn, and so on, . . . , every two warpyarns, and so on, . . . . There are an unlimited number of possiblecombinations, which are all included within the scope of the presentinvention.

In addition, as shown in FIG. 11C, in an alternative embodiment of thepresent invention, the first portion P₀₁ comprises an opaque coating C₀which has been applied to at least a portion of one of the sides of thereinforcing structure 33. Preferably, for the reasons set forth above,the opaque coating is applied to the machine-facing side 52 of thereinforcing structure 33. The opaque coating C₀ can be applied in anyparticular manner or pattern to the machine-facing side 52 of thereinforcing structure 33 as long as the desired passageways 37 andsurface texture irregularities 38 are formed in the backside network35a. Thus, the opaque coating C₀ can be applied randomly, uniformly,regularly, or in some particular pattern. The opaque coating C₀ can beapplied to the reinforcing structure 33 by any means known in the artfor coating articles.

The first portion P₀₁ is generally provided with the first opacity O₁prior to the incorporation of the reinforcing structure 33 into thepapermaking belt 10. Individual yarns can be provided with the firstopacity O₁, by mixing a suitable opaque material with the polyestermaterial which comprises the yarns during the manufacture of the yarns.Alternatively, individual yarns (or portions thereof, can be providedwith the first opacity P₀₁ by coating the individual yarns with anopaque material prior to weaving them into a fabric. Suitable opaquematerials include those which either absorb, scatter, or reflect actiniclight. Examples of materials which absorb actinic light include organicdyes and carbon black. An example of a material which scatters actiniclight is Ti O₂. Materials which reflect actinic light can includemetal(s) which are deposited on, or included in the fabric. The samematerials are also suitable for use in the opaque coating describedabove. Preferably, the opaque material used is opaque to light having awavelength of between about 200 and 400 nanometers.

The reinforcing structure 33 of the present invention defines severalprojected areas which are useful in describing the location of thepassageways 37 and surface texture irregularities 38 in the backsidenetwork 35a of the second surface 35 of the framework 32. As shown inFIGS. 12-18, the reinforcing structure 33 defines at least the followingprojected areas: projected interstitial areas; the previously-definedprojected open area (which is the total of all the projectedinterstitial areas for the reinforcing structure); projected structuralcomponent areas; a projected reinforcing area (which is the total of allthe projected structural component areas for the reinforcing structure);projected warp areas (and an overall projected warp area); projectedweft areas (and an overall projected weft area); projected knuckleareas, including projected machine side knuckle areas; and, a first anda second projected area. In addition, when there is more than one layerof warps or wefts, or the like, there may also be projected areas forthe warp yarns in the first warp layer and the second warp layer, and soforth.

The projected interstitial areas are shown in FIG. 12 as Ap_(i). As usedherein, the term "projected interstitial areas" refers to the individualprojected areas defined by the projection of the interstices 39 of thereinforcing structure 33. In other words, when the reinforcing structure33 is viewed from a direction perpendicular to either side of thereinforcing structure 33, each interstice 39 will provide direct linesof sight through the reinforcing structure which constitute theprojected interstitial areas Ap_(i).

The projected structural component area A_(SC) is shown in FIG. 13. Asused herein, the term "projected structural component area" refers tothe area defined by the projection of an individual structural component40a of the reinforcing structure 33. As used herein, the term "projectedstructural component areas" shall mean the area defined by theprojection of more than one, but not all of the structural components40a of the reinforcing structure 33.

A portion of the projected reinforcing area A_(R) is shown in FIG. 13.As used herein, the term "projected reinforcing area" shall mean thearea defined by the projection of the reinforcing component 40. As shownin FIGS. 12 and 13, the projected reinforcing area A_(R) is essentiallythe opposite of the projected open area A_(O) of the reinforcingcomponent 33, it is the portion of the reinforcing structure 33 whichblocks out lines of sight. The projected reinforcing area A_(R) iscomplementary with the projected open area A_(O) in that together bothcomprise the entire projected area of the reinforcing structure 33.

The projected warp areas Awp are shown in FIGS. 14 and 15. As usedherein, the term "projected warp area" A_(wp) refers to the area definedby the projection of the individual warp yarns 53 of the reinforcingstructure 33. In FIG. 15, the projected warp areas A_(wp) are shown asthe cross-hatched areas which lie between the dotted lines. These dottedlines could also extend above the paper-facing side 51 of thereinforcing structure 33. However, the present invention is generallynot concerned with passageways and surface texture irregularities whichlie above the plane of the paper-facing side 51 of the reinforcingstructure 33. Therefore, when the position of a passageway or surfacetexture irregularity is being described herein with reference to aprojected area, the passageway or irregularity will generally liebetween the paper-facing side 51 of the reinforcing structure 33 and aplane defined by the backside 12 of the belt 10. When it is said that apassageway or a surface texture irregularity "lies within" the projectedwarp areas shown in FIGS. 14 and 15, it can be any place within theareas that are shaded in FIG. 14, or cross-hatched in FIG. 15. Inaddition to the projected warp area defined by each individual warp,there is an "overall projected warp area" A_(wp0) which comprises thetotal for the entire fabric of the individual projected warp areas.

The projected weft areas A_(wt) are shown in FIGS. 16 and 17. As usedherein, the term "projected weft area" A_(wt) refers to the area definedby the projection of the individual wefts 54 of the reinforcingstructure 33. In addition to the projected weft area A_(wt), there is an"overall projected weft area" A_(wt0) (a portion of which is shown inFIGS. 16 and 17) which comprises the total of the individual projectedweft areas A_(wt) for the entire reinforcing structure.

As used herein, the term "projected knuckle area" of the reinforcingstructure 33 refers to the area defined by the projection of one of theknuckles 105 of a woven reinforcing structure. As shown in FIGS.18A-18C, a projected knuckle area A_(K) is the portion of thereinforcing structure 33 where a warp yarn and a weft yarn overlap whichblocks out lines of sight through the reinforcing structure 33. Theprojected knuckle areas can be further classified as projected warpknuckle areas A_(Kwp) (the projected area formed by a warp yarn passingover a weft yarn) or projected weft knuckle areas A_(Kwt) (the projectedarea formed by a weft yarn which passes over a warp yarn). The projectedwarp knuckle areas A_(Kwp) and the projected weft knuckle areas A_(Kwt)can be further classified as projected paper (or paper-facing) side warpknuckle areas A_(Kwp1) or weft knuckle areas A_(Kwt1), and projectedmachine-facing (or machine side) warp knuckle areas A_(Kwp2) or weftknuckle areas A_(Kwt2) (depending on which side of the fabric theknuckles are formed).

A portion of the first projected area A₁ and a portion of the secondprojected area A₂ are shown as cross-hatched areas in FIGS. 11A and 11B,respectively. As used herein, the term "first projected area" A₁ is thearea defined by the projection of the first portion P₀₁ of thereinforcing structure 33 which has the first opacity O₁. The remainderof the reinforcing structure 33 generally has the second opacity O₂ anddefines the second projected area A₂. FIGS. 11A and 11B show that thepassageways 37 in the backside network 35a of the framework 32 arepositioned predominately within the first projected area A₁ (whether thefirst portion P₀₁ be formed by every warp yarn 53 or every alternatingwarp yarn, or by some other portion of the reinforcing structure 33).

The other primary element of the papermaking belt 10 of the presentinvention is the framework 32. The overall characteristics of theframework 32 are shown in FIGS. 2-4. In the preferred embodiment of thepresent invention, the framework 32 is formed by manipulating a mass ofmaterial, which is generally in liquid form, so that the material, whenin solid form, at least partially surrounds the reinforcing structure 33in such a manner that the reinforcing structure 33 is positioned betweenthe top or the first surface 34 of the framework 32 and at least aportion of the bottom or second surface 35 of the framework 32. Inaddition, the material must be manipulated so that the framework 32 hasa plurality of conduits 36 or channels which extend between the firstsurface 34 and the second surface 35 of the framework 32. The materialmust also be manipulated so that the first surface has a paper sidenetwork 34a formed therein which surrounds and defines the openings ofthe conduits 36 in the first surface 34 of the framework 32. Inaddition, the material must be manipulated so that the second surface 35of the framework 32 has a backside network 35a with passageways 37,distinct from the conduits 36, that provide surface textureirregularities 38 in the backside network 35a.

The mass of material which is manipulated to form the framework 32 canbe any suitable material, including thermoplastic resins andphotosensitive resins, but the preferred material for use in forming theframework 32 of the present invention is a liquid photosensitivepolymeric resin. Likewise, the material chosen can be manipulated in awide variety of ways to form the desired framework 32, includingmechanical punching or drilling, curing the material by exposing it tovarious temperatures or energy sources, or by using a laser to cutconduits in the same. The method of manipulating the material which willform the framework 32, of course, will depend on the material chosen andthe characteristics of the framework 32 desired to be formed from themass of material. The preferred method used for manipulatingphotosensitive resin, is controlling the exposure of the liquidphotosensitive resin to light of an activating wavelength.

The relationship between the sides of the papermaking belt 10 of thepresent invention (that is, paper-contacting side 11 and backside 12described above) and the surfaces of the framework 32 are best shown inFIGS. 3 and 4. The first surface 34 of the framework 32 preferably formsthe paper-contacting side 11 of the papermaking belt 10. Thisrelationship will usually exist in most embodiments of the presentinvention since the reinforcing structure 33 is positioned between thefirst surface 34 of the framework 32 and at least a portion of thesecond surface 35 of the framework 32. That is, the first surface 34 ofthe framework 32 generally covers the paper-facing side 51 of thereinforcing structure 33.

The second surface 35 of the framework 32 of the papermaking belt 10 ofthe present invention, however, does not necessarily always form thebackside 12 of the papermaking belt 10. Since the reinforcing structure33 is positioned between the first surface 34 and at least a portion ofthe second surface 35 of the framework 32, the second surface 35 of theframework 32 can either, completely cover the reinforcing structure 33(although this will generally not occur when the papermaking belt ismade by the process described herein); cover only a portion of thereinforcing structure 33; or, cover no portions of the reinforcingstructure 33 and lie entirely within the interstices 39 of thereinforcing structure 33. In the first case, the second surface 35 ofthe framework 32 and the backside 12 of the papermaking belt 10 will bethe same. In the second case, the backside 12 of the papermaking belt 10will be comprised partially of the second surface 35 of the framework 32and partially of the exposed portion of the reinforcing structure 33. Inthe third case, the backside 12 of the papermaking belt 10 will also becomprised partially of the second surface 35 of the framework 32 andpartially of the reinforcing structure 33, but the machine-facing side52 of the reinforcing structure 33 will be completely exposed on thebackside 12 of the papermaking belt 10.

FIG. 2 shows that the first surface 34 of the framework 32 (and thepaper-contacting side 11 of the papermaking belt 10) is comprised of aportion of a network which is designated 32a. As used herein, the term"network" refers to the portions of the framework 32 which surround theconduits 36 and define a net-like pattern. In other words, the network32a is the solid portion of the framework 32. As shown in the enlargedphotographs of the papermaking belt 10 of the present invention, FIGS.34A and 34B, the network 32a has two network surfaces 34a and 35a. Asused herein, the term "network surface" refers to one of the surfaces ofthe network 32a which surrounds the conduits 36. These network surfacesare also referred to herein as the "knuckles" of the framework 32. Theknuckles of the framework 32 are, however, to be distinguished from thepreviously described knuckles formed by the yarns of the reinforcingstructure 33. The term "network surface" was also used in the patentsissued to Trokhan and Johnson, which are incorporated by referenceherein. As used herein, however, the term "network surface" will bemodified by specifying whether the network surface referenced is the"paper side network surface" or the "backside network surface".

The term "paper side network surface", (or "paper side network" forshort) refers to the solid portion of the framework on the top, or thefirst surface 34 of the framework 32. Thus, the surface of the frameworkwhich is referred to as the "network surface" in the patents which areincorporated by reference herein generally corresponds to the paper sidenetwork surface in the present specification. The paper side networksurface is represented by reference numeral 34a in the drawings.

The term "backside network surface" (or "backside network" for short)refers to the solid portion of the framework 32 on the bottom, or thesecond surface 35 of the framework 32. The backside network surface isrepresented in the drawings by reference number 35a.

As shown in FIGS. 2-4, the first surface 34 of the framework 32comprises both the paper side network surface 34a, and first conduitopenings 42. The first conduit openings 42 are the openings of theconduits 36 along the first surface 34 of the framework 32. The secondsurface 35 of the framework 32 comprises both the backside networksurface 35a and second conduit openings 43. The second conduit openings43 are the openings of the conduits 36 along the second surface 35 ofthe framework 32. The paper side network surface 34a and the firstconduit openings 42 in the first surface 34 of the framework 32 willoften be described herein as being "complementary" because together theyrespectively comprise one entire surface of the framework 32. For thesame reason, the backside network surface 35a and the second conduitopenings 43 will likewise be described herein as complementary.

As shown in FIG. 2, the paper side network 34a is macroscopicallymonoplanar, patterned, and continuous. This allows a uniform pattern tobe imparted to the paper web during processing. By "macroscopicallymonoplanar," it is meant that when a portion of the paper-contactingside 11 of the papermaking belt 10 is placed into a planarconfiguration, the paper side network 34a is essentially in one plane.It is said to be "essentially" monoplanar to recognize the fact thatdeviations from absolute planarity are tolerable, but not preferred, solong as the deviations are not substantial enough to adversely affectthe performance of the product formed on the papermaking belt 10. Thepaper side network 34a is said to be "continuous" because the linesformed by the network on the paper side network surface 34a must form atleast one essentially unbroken net-like pattern. The pattern is said tobe "essentially" continuous to recognize the fact that interruptions inthe pattern are tolerable, but not preferred, so long as theinterruptions are not substantial enough to adversely affect theperformance of the product made on the papermaking belt 10.

The conduits (or "deflection conduits") 36 which pass from the firstsurface 34 of the framework 32 to the second surface 35 of the framework32 are shown in FIGS. 2-4. Each conduit 36 defines certain features,which include: a channel portion or a hole, generally designated 41; amouth, or conduit opening (also known as a "gross foramina"), such asfirst conduit opening 42 formed along the first surface 34 of theframework 32; a mouth, or conduit opening, such as second conduitopening 43 formed generally along the second surface 35 of the framework32; and, conduit walls, generally designated 44, which define thedimensions of the conduits 36 in the interior portion of the framework32. (The "interior portion" of the framework is the portion of theframework 32 which lies between the first and second surfaces 34 and35). As shown in FIGS. 2-4, the walls 44 of the conduits 36 form theinterior walls 44a of the framework 32. The interior walls 44a of theframework 32 are the surfaces of the framework 32 which are coterminouswith the walls 44 of the conduits 36. In other words, the walls 44 ofthe conduits 36 have the same or coincident boundaries with the interiorwalls 44a of the framework 32. The second conduit openings 43 aredescribed as being formed "generally along" the second surface 35 of theframework 32 because if one or more passageways 37 intersects with asecond conduit opening 43, at least a portion of the second conduitopening 43 may be displaced so that it actually lies between the firstsurface 34 of the framework 32 and the surrounding portions of thesecond surface 35 of the framework 32. In other words, portions ofsecond conduit openings 43 may lie inward (toward the center of thebelt) from the plane defined by the adjacent portions of the secondsurface 35 of the framework 32.

FIG. 2 shows that the first conduit openings 42 in the first surface 34of the framework 32 are uniform and of a particular geometry. The secondconduit openings 43 in the second surface 35 of the framework 32 arealso of basically the same geometry as the first conduit openings 42.However, as shown in FIG. 34B, the passageways and surface textureirregularities present in the backside network 35a of the framework 32can cause the second conduit openings 43 to be distorted and veryirregular in shape. This distortion is not particularly problematic inthe present invention, however, because the backside network 35a whichsurrounds the second conduit openings 43 does not contact and impress apattern into the paper web during formation.

Although there are an infinite variety of possible geometries for theopenings 42 and 43 of the conduits 36, certain broad guidelines forselecting a particular conduit opening geometry can be stated. Theseguidelines are set forth in Col. 5, line 34 through Col. 10, line 35 ofU.S. Pat. No. 4,528,239, entitled "Deflection Member", which issued toPaul D. Trokhan on Jul. 9, 1985, which is incorporated by referenceherein.

The shape and arrangement of the conduits 36 shown in FIG. 2 are in anespecially preferred form. The shape of the conduit openings, 42 and 43,depicted in these figures is referred to herein as being in a "linearIdaho" pattern. As shown in FIG. 2, the linear Idaho conduits areroughly in the shape of modified parallelograms in cross-section. Theshape of the conduits 36 is described as resembling modifiedparallelograms because in this plan view, each conduit 36 has four sidesin which each pair of opposite sides are parallel, the angle betweenadjacent sides are not right angles, and the corners formed betweenadjacent sides are rounded. Thus, the linear Idaho conduit openings mayalso be described as parallelograms having rounded corners.

The details of the construction of these linear Idaho conduits 36 areshown in FIG. 19. Only a portion of the framework 32 of the papermakingbelt 10 showing the repeating pattern of conduits 36 is shown in FIG.19. In addition, only the paper side network surface 34a on all but oneof the conduits is shown for clarity of illustration. The particularshape of the conduits 36 is arrived at in the manner described below. Aswill be apparent, however, it is possible to vary the sequence of thesteps and arrive at the same result. It is also apparent that thepoints, lines, and circles used to arrive at the shape of the conduits(except to the extent that they form the walls 44 of the conduits 36)will not be actually visible in the conduits 36 constructed by theprocedure described below.

To form a geometrical shape in a linear Idaho pattern, initially, twopoints, P₁ and P₂, are selected which lie a certain distance, d₁, apartfrom one another. The line connecting the two points, P₁ and P₂, will bereferred to as the machine direction axis, or longitudinal axis A_(L),of the conduit. The distance, d₁, between the two points, P₁ and P₂,(which is equal to the length of the longitudinal axis A_(L)), ispreselected. At each of these points, a circle of a given radius, R₁, isdrawn. Next, a line A_(T) is drawn perpendicular to the longitudinalaxis A_(L) of the conduit. This next line A_(T) is drawn through thelongitudinal axis A_(L), so that it bisects the longitudinal axis A_(L).Two points, P₃ and P₄, are then placed equidistant from the longitudinalaxis A_(L) on the second line A_(T). The distance, d₂, between points P₃and P₄ is also preselected. The line connecting points P₃ and P₄, A_(T),will be referred to as the cross-machine direction axis or transverseaxis of the conduit. At both points P₃ and P₄, a circle of a givenradius R₂ is drawn. Although the latter radius, R₂, does not have to beequal to the radius R₁ of the circle drawn earlier, in the preferredpattern shown in FIG. 19, R₁ equals R₂. As a final step, tangent lines,L₁, L₂, L₃, and L₄, are drawn between portions of the four circlespreviously drawn. The tangent lines are drawn so that they are tangentto the portions of the circles which are farthest away from theintersection of the longitudinal axis A_(L) and the transverse axisA_(T). The line which passes around the perimeter of the shape thusdescribed forms the walls 44 of the linear Idaho conduit 36. As shown inFIG. 19, the sides of the first conduit openings are designated 45a,45b, 45c, and 45d, and the rounded corners between adjacent sides aredesignated 46. The corresponding sides of the second conduit openings 43are designated 45e, 45f, 45g, and 45h. The corresponding corners of thesecond conduit openings 43 are designated 46a.

Other suitable shapes for the conduits 36 in the framework 32 of thepapermaking belt 10 of the present invention include, but are notlimited to, the modified hexagon described in the patents issued toTrokhan and Johnson, incorporated herein by reference, and the "Bowtie", or "Sine-Curve" pattern shown in FIG. 20.

Regardless of the shape of the conduit openings, whether they be in theshape of the preferred linear Idaho pattern, or in some other shape, thenumber of conduits 36 per a given area of the belt and the proportionateamount of space occupied by the conduit openings in the framework 32 ofthe papermaking belt 10 of the present invention should be withincertain ranges.

The number of conduits 36 present in the framework 32 is generallyexpressed in terms of the number of conduits per square inch of thetotal surface area of the framework 32. As used herein, the term "totalsurface area of the framework" refers to the sum of the surface area ofeither the paper side network surface 34a and the complementary surfacearea occupied by the first conduit openings 42, or the sum of thesurface area of the backside network surface 35a and the complementarysurface area occupied by the second openings 43. The number of conduits36 present in the framework 32 should preferably be between about 10 andabout 1,000 per square inch.

The proportionate amount of space occupied by the conduit openings isgenerally expressed herein as a percentage of the total surface area ofthe framework 32. It is also common in this specification to express theproportionate amount of space occupied by the complementary networksurfaces of the framework, 34a and 35a, as percentages of the totalsurface area of the framework 32. The space occupied by the paper sidenetwork surface 34a and the backside network surface 35a are generallyreferred to herein as the "knuckle areas" of the respective surfaces ofthe framework 32. These knuckle areas are shown as A_(N1) and A_(N2),respectively, in FIGS. 19A and 19B. The paper side knuckle area (orfirst surface knuckle area) A_(N1) (shaded in FIG. 19A), is theprojection of the paper side network surface 34a in the z-direction intoa plane. The backside knuckle area (or second surface knuckle area)A_(N2) (shaded in FIG. 19B), is the projection of the backside networksurface 35a in the z-direction into a plane. The proportionate amount ofspace occupied by the conduit openings can be derived from the amount ofspace occupied by the knuckle areas of the framework 32. Since the areaoccupied by the openings of the conduits and the area occupied by therespective network surfaces are complementary, the total of the twopercentages is equal to 100%. If either the knuckle areas are known, orif the proportionate amount of space occupied by the conduit openings isknown, the complementary area can be calculated by subtracting the knownpercentage from 100%.

The proportionate amount of space occupied by the first conduit openings42 in the first surface 34 of the framework 32, is preferably betweenabout 30% and about 80% of the total surface area of the framework 32.In other words, the first surface 34 of the framework 32 has about20%-70% knuckle area. The proportionate amount of space occupied by thesecond conduit openings 43 in the second surface 35 of the framework 32is preferably between about 30% and about 80% of the total surface areaof the framework 32. In other words, the second surface 35 of theframework 32 has about 20%-about 70% knuckle area.

The particular arrangement of the individual conduits 36 and spacingsbetween the conduits 36 shown in FIG. 2 is but one possible arrangementof the conduits 36. There are a number of preferred arrangements of theindividual conduits 36 and spacings between the conduits 36. Several ofthese preferred arrangements and spacings are set forth in thediscussion in Col. 8, lines 35-58 of U.S. Pat. No. 4,528,239, entitled"Deflection Member", which issued to Paul D. Trokhan on Jul. 9, 1985,which discussion is incorporated by reference herein. A particularlypreferred arrangement of conduits 36 and spacings between conduits 36,however, is the bilaterally staggered array of openings shown in FIG. 2.In FIG. 2, it is shown that in this particularly preferred arrangementand spacing, the openings 42 of the conduits 36, such as first conduitopenings 42, are of sufficient size and spacing that, in any direction,the edges of the conduits 36 extend past one another.

In an especially preferred embodiment of the papermaking belt 10 of thepresent invention having linear Idaho shaped conduits, the parameters ofthe conduits 36 (that is, the number, size, and arrangement of conduitopenings) are designated herein as a "300 linear Idaho with 35% knucklearea" pattern. The first number of the above designation represents thenumber of conduits 36 present in the framework 32 per square inch. Thus,the framework 32 has 300 conduits per square inch. The second number(i.e., 35% knuckle area) refers to the approximate surface area, orknuckle area, of the paper side network surface 34a. In this preferredembodiment, the papermaking belt is constructed so the surface area, orknuckle area, of the backside network surface 35a is approximately 65%.

The dimensions used in the construction of the conduits 36, as well asthe overall dimensions of the conduits, and the spacing between conduits36 in the preferred 300 linear Idaho 35% knuckle area pattern are shownin FIG. 19. To construct conduits in the 300 linear Idaho 35% knucklearea pattern, the following lengths and radiuses are used: d₁ is 0.0425inches (1.0795) mm, d₂ is 0.024712 inches (0.62785 mm), and R₁ and R₂are both 0.012008 inches (0.3050 mm). The overall dimensions of theopenings of the conduits and the spacing between conduits in the firstsurface 34 of the framework 32 are represented by a series of referenceletters in FIG. 19. In FIG. 19, reference letter "a" represents themachine direction (or "MD") length, or simply the "length" of an openingas illustrated, "b" the length of the opening as measured in thecross-machine direction (or "CD"), or the "width" of the opening, "c"the spacing between two adjacent openings in a direction intermediate MDand CD, "d" the CD spacing between adjacent openings, and "e" the MDspacing between adjacent openings. In this preferred embodiment, "a" is1.6892 millimeters (0.066506 inch), b 1.2379 mm (0.048737 inch), c0.28153 mm (0.011084 inch), d 0.92055 mm (0.036242 inch), and e 0.30500mm (0.012008 inch).

The conduits 36 have a channel portion 41 which lies between the conduitopenings 42 and 43. These channel portions 41 are defined by the walls44 of the conduits 36. The overall characteristics of these channelportions 41 and the walls 44 are shown in FIGS. 2-4. FIGS. 2-4 show thatthe holes or channels 41 formed by the conduits 36 extend through theentire thickness of the papermaking belt 10. In addition, as shown inFIG. 2, the conduits 36 are generally discrete. By "discrete", it ismeant that the conduits 36 form separate channels, which are separatedfrom each other by the framework 32. The separation of the conduits 36is particularly evident in the plan view of FIG. 2. The conduits 36 aredescribed as being "generally" discrete, however, because as shown inFIG. 34B, for example, the conduits 36 may not be completely separatedfrom each other along the second surface 35 of the framework 32 whenpassageways 37 are present in the backside network 35a. The conduits 36are also shown to be isolated in that there is no connection within thebody of the papermaking belt 10 between one conduit 36 and another. Thisisolation of one conduit 36 from another is particularly evident in thecross-sectional views of FIGS. 3 and 4. Thus, transfer of material (forexample, fluids, such as the water removed from the paper web) from oneconduit 36 to another is generally not possible unless the transfer iseffected outside the body of the papermaking belt 10, or unless as inthe belt shown in FIG. 34B, for instance, the transfer is effected inthe passageways 37 along certain portions of the backside 12 of thepapermaking belt 10.

FIGS. 3 and 4 show the orientation of the conduits 36 in the framework32. As shown in FIGS. 3-4, the conduits 36 have a vertical axis which isdesignated A_(V). The vertical axis A_(V) is an imaginary line whichpasses through the center of each of the conduits 36 between the firstconduit openings 42 and the second conduit openings 43. The orientationof the vertical axis A_(V) determines the orientation of the conduits 36in the framework 32 relative to the surfaces 34 and 35 of the framework32. Thus, it should be understood that in the present invention, thevertical axis A_(V) does not always have a truly vertical orientation;it is merely relatively vertical with respect to the longitudinal andtransverse axes A_(L) and A_(T) of the conduits 36. The orientation ofthe vertical axis A_(V) of the conduits 36 can range widely from anorientation in which the vertical axis A_(V) is oriented generallyperpendicular to the first and second surfaces 34 and 35 of theframework 32 to an orientation in which the vertical axis A.sub. V isoriented such that the conduits 36 are formed at an angle in theframework 32. Preferably, however, as shown in FIGS. 3 and 4, thevertical axis A_(V) of the conduits 36 is generally approximatelyperpendicular to the first and second surfaces 34 and 35 of theframework 32.

The profile of the cross-section of the walls 44 of the conduits 36 isshown on enlarged scale in FIG. 21. The profile of the walls 44 of theconduits 36 can be relatively straight, curved, partially curved andpartially straight, or irregular when viewed in cross-section. It shouldbe noted that in the drawing figures other than FIG. 21 which show thewalls 44 of the conduits 36, the walls 44 of the conduits 36 are shownschematically as straight lines for ease of illustration. However, asshown in FIG. 21, it is believed that the profile of the walls 44 of theconduits 36 may be nonlinear from the top surface 34 of the framework 32to the bottom surface 35 of the framework 32.

As shown in FIG. 21, the profile of the walls 44 of the conduits 36 isessentially a straight line (in the region represented by referencenumeral 47) from the first surface 34 of the framework 32 to a regionalong the walls 44, which begins approximately at the points which havebeen marked with reference numeral 48. The points marked with referencenumeral 48 are the approximate places where the paper-facing side 51 ofthe reinforcing structure 33 is encountered. At the points 48 at whichthe paper-facing side 51 of the reinforcing structure 33 is encountered,the profile of the walls 44 of the conduits 36 is less well-defined. Atthis point, the profile of the walls 44 of the conduits 36 generallybecomes somewhat irregular. The portion of the walls 44 of the conduits36 which displays an irregular profile is designated by referencenumeral 49 in FIG. 21. The irregular portion 49 of the profile of thewalls 44 of the conduits 36 is formed during the curing of the liquidphotosensitive resin into the framework 32. The ultraviolet light usedto cure the resin is supplied by light sources which are positionedabove the paper-facing side 51 of the reinforcing structure and theliquid photosensitive resin coating on top of the paper facing side 51.The light rays diffuse or scatter to a certain extent when theyencounter the strands of the reinforcing structure 33 causing thephotosensitive resin to cure in an irregular manner. Thus, the exactlocation of the beginning of the irregular portion of the walls 44 willvary depending on the place at which the reinforcing structure 33 isencountered.

The relationship of the walls 44 of the conduits 36 relative to eachother (i.e., the taper of the walls) can vary from cases in which thewalls 44 are parallel to each other to cases in which the walls 44 aretapered either outwardly or tapered inwardly from the top surface 34 ofthe framework 32 to the bottom surface 35 of the framework 32. Inaddition, because the walls 44 of the conduits 36 form the interiorwalls 44a of the framework 32, as shown in FIGS. 2-4, the interior walls44a of the framework 32 can also be tapered. As used in reference to thetapering of the walls 44 of the conduits 36 or the interior walls 44a ofthe framework 32, the term "outwardly" refers to the relationship inwhich the distance between the opposed walls 44, or interior walls 44achanges from a lesser value to a greater value. The term "inwardly"refers to the opposite relationship (that is, a relationship in whichthe distance between the walls 44, or interior walls 44a changes from agreater to a lesser value).

FIGS. 1A and B show one embodiment of the conduits 36 in which the walls44 of the conduits 36 are parallel to each other. FIGS. 2-4 show apreferred embodiment of the present invention in which the walls 44forming the inside of the conduits 36 are tapered inwardly from the topsurface 34 of the framework 32 to the bottom surface 35 of the framework32. When the walls 44 of the conduits 36 are tapered either inwardly oroutwardly, the interior walls 44a of the framework 32 will bear theopposite relationship to each other. Thus, as shown in FIGS. 2-4, whenthe walls 44 of the conduits 36 are tapered inwardly from the topsurface 34 of the framework 32 to the bottom surface, the interior walls44a will be tapered outwardly from the top surface 34 of the framework32 to the bottom surface 35. The tapering of the walls 44 and interiorwalls 44a is controlled by collimating the light used to cure thephotosensitive resin.

Preferably, the interior walls 44a of the framework 32 are taperedoutwardly from the top surface 34 of the framework 32 to the bottomsurface 35 of the framework 32 in an amount such that the surface areaof the paper side network 34a is less than about 70% of the totalsurface area of the framework 32, and the surface area of the backsidenetwork 35a in the second surface 35 of the framework 32 is at leastabout 45% of the total surface area of the framework 32. In anespecially preferred embodiment, the interior walls 44a are tapered suchthat the surface area of the paper side network 34a (first surfaceknuckle area A_(N1)) is approximately 35% of the total surface area ofthe framework, and the surface area of the backside network 35a (secondsurface knuckle area A_(N2)) is approximately 65% of the total surfacearea of the backside 12 of the papermaking belt 10 of the presentinvention prior to the formation of the passageways 37 in the backsidenetwork 35a. In this especially preferred embodiment of the presentinvention, the angle of the taper, a_(T) shown in FIG. 21, of the walls44 of the conduits 36 is approximately 15 degrees from vertical.

The relationship between the framework 32 and the reinforcing structure33 is shown in FIGS. 3 and 4. As shown in FIGS. 3 and 4, the reinforcingstructure 33 is generally located more near the backside 12 of thepapermaking belt 10 than the paper-contacting side 11 of the belt. Whileit is possible to create a belt in which the reinforcing structure 33 islocated more near the paper side 11, such a construction is notpreferred.

There are three primary reasons the reinforcing structure 33 is locatedmore near the backside 12 of the papermaking belt 10. One reason is thatthe reinforcing structure 33 is generally placed adjacent to a castingsurface during formation, and as a result, only a limited amount ofresin is generally present between the reinforcing structure 33 and thecasting surface. This can, however, be altered without departing fromthe scope of this invention. Another reason is that it is frequentlypreferable for the reinforcing structure 33 to serve as the wear surfaceor machine-contacting surface when the portions of the resin framework32 along the backside 12 of the papermaking belt 10 wear thin becausethe reinforcing structure 33 provides more a durable surface forcontacting the papermaking equipment over which the papermaking belt 10passes than does the hardened polymeric resin which comprises theframework 32. A final reason is that a portion of the resin framework 32must cover the reinforcing structure 33 to form conduits 36 of thedesired pattern and depth on top of the paper-facing side 51 of thereinforcing structure 33. The portion of the resin framework 32 coveringthe reinforcing structure 33 is referred to as "the overburden" and isdesignated as t₀ in FIG. 21. The overburden enables the conduits 36 toadequately serve their purpose of providing an area into which thefibers in the paper web can be deflected so that these fibers can berearranged without the interference of the strands of the reinforcingstructure 33.

When it is said that the reinforcing structure 33 is located more nearto the backside 12 of the papermaking belt 10, the particular dimensionsinvolved can vary. In the preferred embodiment of the papermaking belt10 of the present invention, the typical preferred woven element withstacked warp strands has a thickness of between about 10 mils and about37 mils (0.254 mm and 0.94 mm). The thickness of the resin overburden t₀is between about 4 mils and about 30 mils (0.102 mm and 0.762 mm). Whenthe overburden t₀ is within this preferred range, the compositepapermaking belt 10 is generally between approximately 14 and 67 milsthick (0.356 mm and 1.70 mm). Other applications could require that theoverburden t₀ be between about 2 mils and about 250 mils thick (0.051 mmand 6.35 mm). This would, of course, change the overall thickness of thecomposite papermaking belt 10 accordingly.

FIGS. 3 and 4 show the characteristics of the backside 12 of thepapermaking belt 10 and the second surface 35 of the framework. As shownin FIGS. 3 and 4, the papermaking belt 10 has a textured backside 12. Itis this textured backside 12 which is also referred to herein as"backside texturing", or "backside texture") which is of primaryimportance in the present invention. As used herein with relation to thebackside 12 of the papermaking belt 10, the term "texture" refers to thecharacteristic of the backside 12 created by discontinuities ornonplanar interruptions in what would ordinarily be a smooth or planarsurface. These discontinuities or nonplanar interruptions can compriseprojections from the plane of such a surface or depressions in such aplanar surface.

FIGS. 22A through 22C show that a backside texture can be provided bydifferent portions of a papermaking belt when the belt comprises aframework and a reinforcing structure. It should be understood, however,that the particular types of backside texture shown in FIGS. 22A through22C will not necessarily be found in the papermaking belt 10 of thepresent invention. The particular type of backside texture likely to beformed in the papermaking belt of the present invention is shown inFIGS. 3, 4, 11A, 11B, and in some of the other figures which follow.FIGS. 22A through 22C show that the backside texture in general can beprovided by: the passageways 37 that provide surface textureirregularities 38 in the backside network 35a of the second surface 35of the framework 32; by the characteristics of the machine-facing side52 of the reinforcing structure 33; or, by both the passageways 37 thatprovide surface texture irregularities 38 and the characteristics of themachine-facing side 52 of the reinforcing structure 33. The definitionsof these terms and a description of the characteristics of themachine-facing side 52 of the reinforcing structure 33 are providedbelow. Each of the alternative ways the backside texture can be providedare then examined with reference to FIGS. 22A-22C.

As used herein, the term "passageways" means spaces through which airmay pass. The term "passageways" shall not be construed to includespaces which are of any particular shape and size. Thus, the passageways37 described herein are not limited to spaces which resemble tunnels andthe like in shape.

As used herein, the term "surface texture irregularities" (or simply"irregularities") refers to any discontinuity or nonplanar interruptionsin an ordinarily smooth or planar surface, such as projections from theplane of a smooth surface and/or depressions in such a surface. Theirregularities 38 comprise those portions which constitute nonregular oruneven portions in the backside network 35a of the second surface 35 ofthe framework 32. The surface texture irregularities 38 can be anydiscontinuities, or breaks in the resinous material which forms thebackside network surface 35a, or any portions of the backside networksurface 35a where resin has been removed or added to the backsidenetwork surface 35a.

The characteristics of the machine-facing side 52 of the reinforcingstructure 33 which may form or contribute to form the backside textureare shown in FIGS. 22A through 22C. As shown in FIGS. 22A through 22C,the structural components 40a such as the knuckles and yarns of thewoven reinforcing structure define several planes which are referencesfor describing the backside texture of the belt 10. The backside 12 ofthe papermaking belt 10 of the present invention defines a plane whichis designated P_(b). The plane P_(b) defined by the backside of the beltis a plane which, if the backside 12 of the papermaking belt 10 of thepresent invention were placed on a flat surface, would lie in the sameplane as the flat surface. The knuckles of the paper-facing side 51 ofthe reinforcing structure 33 (such as paper side knuckles such as105_(b1)) define a plane which is designated P_(k1). The plane P_(k1) isreferred to herein as "the plane defined by the paper-facing side of thereinforcing structure." The knuckles of the machine-facing side 52 ofthe reinforcing structure 33 (such as backside knuckles 105_(b2)) definea plane which is designated P_(k2). The plane P_(k2) is referred toherein as "the plane defined by the machine-facing side of thereinforcing structure."

As shown in FIGS. 22A, B, and C, the profile of the machine-facing side52 of the reinforcing structure 33 cross-section has a specific contouror shape. As shown in these figures, the contour of the machine-facingside 52 of a woven reinforcing structure 33 is defined by some of thewarp yarns 53 and some of the weft yarns 54 (which comprise thestructural components 40a of the reinforcing structure 33). In addition,FIGS. 22A, B, and C show that portions of some of the warp yarns 53 andsome of the weft yarns 54 on the machine-facing side 52 of thereinforcing structure 33 form raised portions 120. As used herein, theterm "raised portions" refers to those portions of the warp yarns orweft yarns, or other structural components 40a that lie in themachine-facing side 52 of the reinforcing structure 33 and are disposedinward of the plane defined by the machine-facing side of thereinforcing structure P_(k2).

As used with reference to the planes and the raised portions 120described above, the term "inward" means from either the paper side 11of the papermaking belt 10 or the backside 12 of the papermaking belt 10toward the center of the papermaking belt 10 (i.e., toward an imaginaryline which lies midway between the paper side 11 and the backside 12).With relation to the above-described planes, the term "outward" meansfrom the center of the papermaking belt toward either the paper side 11of the papermaking belt 10 or the backside 12 of the papermaking belt10. The raised portions 120 in FIGS. 22A-22C are more specifically shownto be formed by those portions of the warp yarns 53 and the weft yarns54 which lie in the machine-facing side 52 of the reinforcing structure33 between the machine side knuckles, such as knuckles 105b₂.

In the preferred multilayer woven reinforcing structure 33 shown inFIGS. 22A, B, and C, the raised portions 120 are generally formed byportions of the warp yarns 53 of the second warp layer D, together withportions of the interwoven weft yarns 54. More specifically, in thepreferred reinforcing structure 33, the raised portions 120 will beformed by those portions of the warp yarns 53 in the second warp layer Dand by those portions of the weft yarns 54 which lie both in themachine-facing side 52 of the reinforcing structure 33 and between thoseportions of the same yarns which form the machine-side knuckles 105₂. Inaddition, as shown in FIG. 22D, when the reinforcing structure 33 iscomprised of yarns having round cross-sections, and the bottoms of theyarns may lie in the plane P_(k2), some of the raised portions 120 willbe formed by portions on the sides of the yarns which due to thecurvature of the cross-section of the yarns, are spaced away from theplane defined by the machine-facing side of the reinforcing structureP_(k2). These are referred to as "raised perimeter portions" , and aredesignated by reference numeral 120a in FIG. 22D. FIG. 22D shows that inthe particular cross-section shown, these raised perimeter portions 120aare positioned within the projected warp areas A_(wp) of the warp yarns53 in the second warp layer D.

FIGS. 22A-22C also show that certain of the raised portions, theinwardly-spaced raised portions numbered 120', are spaced inward agreater distance from the plane defined by the machine-facing side ofthe reinforcing structure P_(k2) than other raised portions 120. FIGS.22A-C show that in the preferred multilayer reinforcing structure 33,along the cross-section shown, it is believed that some of theinwardly-spaced raised portions 120' are formed by the warp yarns 53 inthe second warp layer D. FIGS. 22A-C show that the points which form thebottom 53' of these warp yarns 53 form a surface, the "raised surface",which defines a plane P_(r). The plane P_(r) is referred to as the planedefined by the raised portions which form the raised surface.

It should be noted in reference to the drawing figures, that thedistance the warp yarns 53 in the second warp layer D are spaced inwardfrom the plane defined by the machine-facing side of the reinforcingstructure P_(k2) has been somewhat exaggerated in FIGS. 22A-C, and insome of the other figures as well, for purposes of illustration. Itshould be understood that in some variations of the reinforcingstructure 33, these warp yarns 53 may be spaced inward in differentamounts. As shown in the variation of the reinforcing structure 33depicted in FIG. 22D, the warp yarns 53 in the second warp layer D mayeven lie in the same plane as the plane defined by the machine-facingside of the reinforcing structure P_(k2). In that case, they will not beinwardly-spaced at all.

The alternative ways in which the passageways 37, the surface textureirregularities 38 and the characteristics of the machine-facing side 52of the reinforcing structure 33, can as a general matter, contribute toform the backside texture are shown in FIGS. 22A-22C. One way that atexture on the backside 12 of a papermaking belt can be provided isshown in FIG. 22A. In FIG. 22A, the texture is provided entirely by thepassageways 37 that provide surface texture irregularities 38 in thebackside network 35a of the framework 32. As shown in FIG. 22A, thesecond surface 35 of the framework 32 completely covers the reinforcingstructure 33 when the backside texture 12 is provided entirely by thepassageways 37 and the irregularities 38. While this type of texturingcan be created using methods other than the method described herein, itwill generally not be created when making a papermaking belt using theprocess described herein.

As used herein, in reference to the surfaces of the framework 32, theterm "covers" means that the side of the reinforcing structure 33 inissue is positioned completely between the first and second surfaces 34and 35 of the framework 32. The surfaces of the framework 32 areconsidered herein to "cover" the side of the reinforcing structure 33 inissue when they are so positioned even though there are portions of thereinforcing structure 33 which lie within the conduits 36, and as aresult will not have a resinous material on either side.

As shown in FIGS. 22B and 22C, the backside texture can be providedpartially by the passageways 37 and irregularities 38 and partially bythe contour of the machine-facing side 52 of the reinforcing structure33. FIG. 22B shows one alternative situation in which the second surface35 of the framework 32 generally does not cover any portions of thereinforcing structure 33 so that the machine-facing side 52 of thereinforcing structure 33 is exposed. FIG. 22C shows another alternativesituation in which the second surface 35 of the framework 32 coversportions of the machine-facing side 52 of the reinforcing structure 33,and leaves other portions of the reinforcing structure 33 exposed.

The types of backside texturing shown in FIGS. 22A through 22C are thethree basic types of backside texturing. These types of backsidetexturing are referred to for convenience as "positive backsidetexture"; "negative backside texture"; and a combination of both"positive and negative backside texture".

By "positive backside texture", as shown in FIG. 22A, it is meant thatthe passageways 37 extend from the plane P_(b) defined by the backside12 of the belt 10 toward the plane defined by the machine-facing side ofthe reinforcing structure P_(k2). As shown in FIG. 22A, in the case ofpositive texturing, the plane defined by the machine-facing side of thereinforcing structure P_(k2) lies inward of the plane defined by thebackside of the papermaking belt P_(b). Thus, the reinforcing structure33 is positioned completely between the first surface 34 of theframework 32 and the second surface 35 of the framework 32.

Another, and perhaps an easier way of looking at positive backsidetexture is to look at the relationship between the passageways 37 andirregularities 38 and the plane defined by the machine-facing side ofthe reinforcing structure P_(k2), rather than at relationship thepassageways 37 and the surface texture irregularities 38 form with theplane defined by the backside of the papermaking belt, P_(b). In thecase of positive backside texture, as shown in FIG. 22A, the passageways37 are positioned outward of the plane defined by the machine-facingside of the reinforcing structure P_(k2). The surface textureirregularities 38 extend outward from the plane defined by themachine-facing side of the reinforcing structure P_(k2).

By "negative backside texture", as shown in FIG. 22B, it is meant thatthe passageways 37 extend inward from the plane defined by themachine-facing side of the reinforcing structure P_(k2) toward the planedefined by the paper-facing side of the reinforcing structure P_(k1). Inpapermaking belts which are exclusively negatively textured, the planedefined by the backside of the papermaking belt P_(b), and the planedefined by the machine-facing side of the reinforcing structure P_(k2)will be the same.

By "positive and negative backside texture", as shown in FIG. 22C, it ismeant that both types of passageways described above are present. Thus,some of the passageways 37 are disposed inward of the plane defined bythe machine-facing side of the reinforcing structure P_(k2), and some ofthe passageways 37 are positioned outward from the plane defined by themachine-facing side of the reinforcing structure. In the case ofpositive and negative backside texture, the plane defined by themachine-facing side of the reinforcing structure P_(k2) lies inward ofthe plane defined by the backside of the papermaking belt P_(b).

It is apparent from an examination of the three figures discussed abovethat the wear surface of a papermaking belt having the different typesof backside texture will differ.

As shown in FIG. 22A, the wear surface of belts which have a positivebackside texture will (at least at first) be comprised entirely of aresinous material. When the jagged projections comprising the surfacetexture irregularities 38 travel over the machinery employed in thepapermaking operation, after many revolutions of the belt 10, theseprojections will tend to wear off so that at some point the wear surfacewill become virtually the same as the plane defined by themachine-facing side of the reinforcing structure P_(k2). The new wearsurface will comprise a combination of the machine-facing side 52 of thereinforcing structure 33 and the resin from the framework 32 which hasbeen worn to a level even with the plane P_(k2). At this point, therewill be a very limited number of passageways 37 for air to pass throughalong the second surface 35 of the framework 32.

As shown in FIG. 22B, the initial wear surface of the belts which have anegative backside texture will generally be solely comprised of portionsof the machine-facing side 52 of the reinforcing structure 33. In thecase of negative texturing, the initial wear surface will thus becomprised of polyester (or one of the other materials specified above)which is generally more durable than the resinous material whichcomprises the framework 32. In addition, as shown in FIG. 22B,negatively textured belts may have passageways such as 37', which extendinwardly from the machine-facing side 52 of the reinforcing structure33. When the belt is worn so that the wear surface coincides with themachine-facing side 52 of the reinforcing structure 33, thesepassageways 37' will still provide openings along the backside 12 of thebelt. Thus, belts having a negative backside texture will generallycontinue to allow air to escape across their backside 12 to a certainextent after having become worn.

As shown in FIG. 22C, the wear surface of the belts which have acombination of both negative and positive texture will, at least atfirst be comprised entirely of the resinous material which comprises theframework 32. When the jagged projections which comprise this resinousmaterial wear off, the wear surface, as in the case of the belt shown inFIG. 22A, will, become virtually the same as the plane defined by themachine-facing side of the reinforcing structure P_(k2). One differencebetween the belts shown in FIGS. 22A and 22C, however, is that becauseof the negative texturing there will still be passageways 37 in thelatter belt after the positive texture has worn off. For this reason, itis believed that it is generally be preferable to have at least somenegative texturing in the preferred embodiment of the present inventionto preserve a textured wear surface on the backside after the initialtexture has been worn down.

In the present invention, the texture is formed on the backside 12 ofthe papermaking belt 10 by exposing the liquid photosensitive resin tolight of an activating wavelength through the reinforcing structure 33.The first portion P₀₁ of the reinforcing component 40 prevents portionsof the photosensitive resinous material from curing to form passageways37 and surface texture irregularities 38 in the backside network 35a ofthe second surface 35 of the framework 32. The location,characteristics, and distribution of the passageways 37 and theirregularities 38 in the papermaking belt are, therefore, generallydescribed with respect to the reinforcing structure 33. The definitionsof several terms will be provided which will serve as references whendescribing the location, characteristics, and distribution of thepassageways 37 and the surface texture irregularities 38 with respect tothe reinforcing structure 33.

As shown in FIGS. 12 and 12A, the passageways 37 and the surface textureirregularities 38 each define projected areas. It is to be understoodthat the passageways 37 and surface texture irregularities 38 are shownin a certain manner in FIGS. 12 and 12A for purposes of the followingdiscussion and that the types of passageways 37 and irregularities 38shown will not necessarily be found in all, or in any embodiments of thepapermaking belt of the present invention. The projected area of thepassageways 37 shown in FIGS. 12 and 12A is represented by referenceletter A_(p). As used herein, the projected area of a passageway 37refers to the area defined by the projection of the passageway 37 in thez-direction. The projected area of the irregularity 38 shown in FIGS. 12and 12A is represented by reference letter A_(i). As used herein, theprojected area of a surface texture irregularity 38 refers to the areadefined by the projection of the irregularity 38 in the z-direction.

As used in this specification, when a passageway 37 or a surface textureirregularity 38 (or the projected area of a passageway 31 or a surfacetexture irregularity 38) is described as being "aligned with", "lyingwithin", or "positioned within", or other similar terms with respect toone of the projected areas of the elements of the reinforcing structure33 (or the framework 32), it is meant that the passageway orirregularity lies within the boundaries of the projected area in allplanes into which the element in issue could be projected in thez-direction. In other words, a passageway or an irregularity which "lieswithin" a projected area could be positioned above the element whichdefines the projected area, or below the element which defines theprojected area, or, even partially above, and partially below theelement. In addition, portions of the passageway or irregularity couldlie within one or more planes into which the element has been projectedin the z-direction.

FIGS. 12 and 12A show several of the possible locations for thepassageways 37 and the surface texture irregularities 38 describedabove. Examining FIGS. 12 and 12A from left to right, the firstpassageway 37 shown lies partially within a projected warp area A_(wp).Part of this passageway 37 also lies outside of the projected warp areaA_(wp). To the right of the first passageway 37 is an irregularity 38.The irregularity 38 shown in FIGS. 12 and 12A lies within a projectedwarp area A_(wp). To the right of the irregularity 38 is a thirdpassageway 37. The third passageway lies entirely within a projectedinterstitial area A_(pi). A fourth passageway 37 is shown to the rightof the third passageway 37. The fourth passageway 37 lies entirelywithin a projected warp area A_(wp).

It should be understood that when a passageway 37 or a surface textureirregularity 38 is described with reference to a projected area, thismeans that the position of the element of in issue is generally locatedas specified relative to the projected area. There may, however, besmall portions of the passageway 37 or irregularity 38 which will notcorrespond exactly with the area in issue. These slight variances in theactual position of the element from the projected areas can beattributed to at least two factors. One factor is the fact that theelements involved (such as the passageways and the irregularities) areextremely small and minor variations in the position of an element willbe exaggerated with respect to the projected areas. This may cause theelement to be slightly outside of the boundaries of the projected area.The second factor results from the fact that the position of thepassageways 37 and the surface texture irregularities 38 are sometimesestablished by the manner in which the light rays which cure the liquidphotosensitive resin comprising the framework 32 pass through thereinforcing structure 33. The direction these light rays travel is notalways solely in the z-direction, and as a result, the projection of theabove-described areas from the direction of the light source may beslightly different from the projection of the same areas in thez-direction.

The characteristics of the passageways 37 and the surface textureirregularities 38 are best discussed with relation to FIG. 21. As shownin FIG. 21, there is a relationship between the passageways 37 and thesurface texture irregularities 38. The passageways 37 are openings forfluid, or more specifically, air, or air and water, to pass along thesecond surface 35 of the framework 32. When the passageways 37 areformed in the backside network 35a, they provide the surface textureirregularities 38. The irregularities 38, therefore, are the portions ofthe backside network 35a of the framework 32 which surround thepassageways 37. In the general sense, however, the passageways 37themselves comprise surface texture irregularities because they are alsodiscontinuities or irregularities in the backside network 35a of theframework 32.

As shown in the FIG. 21, both the passageways 37 and the irregularities38 are distinct from the conduits 36 which pass through the framework32. By "distinct" from the conduits, it is meant that the passageways 37and the irregularities 38 which comprise departures from the otherwisesmooth and continuous backside network 35a of the framework 32 are to bedistinguished from the holes 41 formed by the conduits 36. In otherwords, the holes 41 formed by the conduits 36 are not intended to beclassified as passageways or surface texture irregularities.

The physical characteristics of the individual passageways 37 are shownin FIG. 21. It is to be understood that FIG. 21 is an exaggeratedschematic view of a portion of a papermaking belt which showspassageways 37 and surface texture irregularities 38 of a variety ofdifferent shapes. Thus, while the variety of the backside texturingshown in FIG. 21 is useful in describing the general characteristics ofthe passageways 37 and irregularities 38, the particular backsidetexturing shown in FIG. 21 may not actually be found in the papermakingbelt 10 of the present invention. The particular backside texturing of agiven papermaking belt will depend upon the method used to make thebelt. These particular textures will be discussed generally herein, andin conjunction with the method of making the papermaking belt of thepresent invention described herein. Following the description of themethod of making the papermaking belt, the backside texture of arepresentative papermaking belt will be discussed in conjunction withthe enlarged photographs of one belt constructed in accordance with thatmethod.

As shown in FIG. 21, the passageways 37 can have sides, which aredesignated generally by reference numeral 66. These sides can have aninfinite number of different shapes. They can be curved or relativelystraight when viewed in cross-section, or partially curved and partiallystraight. Oftentimes, however, the sides 66 of the passageways 37 willbe so irregular that they are not capable of precise definition.

As shown in FIG. 21, the sides 66 of the passageways 37 can range fromrelatively vertical (i.e., oriented in the z-direction) to relativelyhorizontal (oriented in the x and y directions). The angle that a side66 forms relative to the z-direction has been designated as a_(s) inFIG. 21. It is to be understood, however, in the case of a passageway 37which has curved or irregular sides, the size of angle a_(s) will varydepending on the reference points used to measure the angle a_(s) formedby the side 66.

Further, each passageway 37 can have various numbers of different sides66. The number of sides 66 can vary from essentially one continuouscurved wall to virtually an infinite number of sides of variouscross-sections. In the simplified cross-section shown in FIG. 21, someof the passageways 37 appear to have sides 66 which resemble interiorwalls, or walls 66a. In addition, some of the passageways 37 which haverelatively vertical walls 66a will have a side which resembles a roof,66b. One side of the passageways 37, however, will always be open. Theopen sides are designated 66c in FIG. 21.

In addition, although the passageways 37 are generally extremely minute,they have a finite height h_(p), width w_(p), spacing s_(p), andcross-sectional area A_(xp).

As shown in FIG. 21, the height h_(p) of a passageway 37 is thedistance, measured in the z-direction, from the plane defined by thebackside of the belt P_(b) to a point, such as 66d, on the interior ofthe passageway 37. As shown in FIG. 21, the height h_(p) of differentportions of an individual passageway 37 may vary across the width of thepassageway 37. In addition, the height h_(p) of the various passageways37 in the backside network 35a of the second surface 35 can vary frompassageway to passageway.

The width w_(p) of a passageway 37 is the distance, measured in somedirection in the X-Y plane, depending upon the cross-section taken,between two points lying on the opposite side walls 66a of thepassageway 37. If the side walls are formed by a single curved surface,the width w_(p) of the passageway is the distance measured in the X-Yplane between two points on opposite sides of the curved surface. Asshown in FIG. 21, the width of a different portions of an individualpassageway 37 may vary depending on the portion of the passageway 37 atwhich the width is measured. In addition, the width of the variouspassageways 37 in the backside network 35a of the second surface 35 canvary from passageway to passageway.

The cross-sectional area of a passageway A_(xp) is represented by across-hatched area in FIG. 21. The cross-sectional area of a passagewayA_(p) is the area measured on a given cross-section, of the interiorportion of the passageway 37 which is bounded by an imaginary line whichruns along the plane defined by the backside of the belt P_(b). Thecombined cross-sectional areas A_(pT) of the individual passageways 37is important in that it is these areas through which air escapes whenthe papermaking belt of the present invention travels over a vacuum boxduring the papermaking process.

The spacing between adjacent passageways 37 is represented by referenceletter s_(p) in FIG. 21. The spacing s_(p) between adjacent passageways37 is defined herein with relation to two points of reference which lieon the sides of the irregularities 38 which border the passageway 37 inissue. These two points, shown as 109 in FIG. 21, lie on the sides ofthe irregularities 38 which are referred to herein as the coterminoussides of the irregularities 38. The coterminous sides of theirregularities 38, designated 67a, are referred to as such because theyalso form the sides 66 of the neighboring passageways 37. The tworeference points 109 chosen are those points on the coterminous sides67a which are the shortest distance measured in the z-direction from theplane defined by the backside of the belt P_(b). In FIG. 21, the tworeference points 109 actually lie in the plane P_(b), but this will notalways be the case. The spacing s_(p) between adjacent passageways 37,shown by the arrow in FIG. 21, is the distance measured in the X-Y planebetween the reference point 109 on the coterminous side 67a of theirregularity 38 which lies between the passageways in issue to the nextadjacent reference point 109 which lies on the opposite coterminous side67 a of the same irregularity 38.

The overall pattern of spacing between the passageways 37 determines thedistribution of the passageways 37. The passageways 37 can bedistributed in an unlimited number of ways across the backside network35a of the framework 32. The distribution of the passageways 37 can, forinstance, be random, uniform, regular, or in some particular pattern.

An example of randomly-spaced passageways 37 are the passageways 37 ofthe belt 10 with a combination of positive and negative texturing shownin FIG. 22C. As used herein, the term "uniform" means that the density(or number) of passageways 37 is approximately the same over the entiresurface, even though the passageways 37 do not form any particularpattern. As used herein, the term "regular" means that the spacingbetween adjacent passageways s_(p) is approximately the same across theentire backside network 35a. An example of regularly-spaced passageways37 are the passageways 37 of the belt 10 shown in FIGS. 3 and 4. Thebelt 10 shown in FIGS. 3 and 4 also serves as an example ofuniformly-spaced passageways in that the density of passageways isapproximately the same over the entire surface of the backside network35a. The spacing between adjacent passageways 37 in the belt 10 shown inFIGS. 3 and 4 is sufficiently similar that the spacing of thepassageways 37 shown therein could also be considered to be in apattern.

The passageways 37 may also be distributed across "generally all"portions of the second surface 35 of the framework 32. By this it ismeant that the passageways 37 can be found on any portion of thebackside network surface 35a; and that there is no particular area, orareas, of the backside network surface 35a from which the passageways 37are excluded. Thus, in the case where the reinforcing structurecomprises a woven element, the passageways 37 can be located in theprojected reinforcing area A_(R) or in the projected open area A₀ of thereinforcing structure. By specifying that the distribution is across"generally all" of the backside network 35a, rather than across "all" ofthe backside network 35a, it is meant that while the passageways 37 canbe found at virtually any particular place on the backside network 35a,the passageways 37 do not necessarily cover the entire backside network35a.

The physical characteristics of the individual surface textureirregularities 38 are shown in FIG. 21. In addition, a generaldescription of surface texture irregularities is found in Broadston,Marks' Standard Handbook for Mechanical Engineers, "Surface-TextureDesignation, Production, and Control," (McGraw-Hill 1967) pp. 13-106 to13-112, which is incorporated herein by reference. As shown in FIG. 21,the sides of the surface texture irregularities 38 are generallydesignated 67. The surface texture irregularities 38 of the presentinvention (like the passageways) can have sides 67 with an infinitenumber of different shapes. As in the case of the passageways, the sides67 of the irregularities 38 can be curved or relatively straight whenviewed in cross-section, or partially curved and partially straight.Oftentimes, however, the sides 67 of the irregularities 38 are soirregular that they are not capable of precise definition.

As shown in FIG. 21, the sides 67 of the irregularities 38 can rangefrom relatively vertical (i.e., sloped in the z-direction) to relativelyhorizontal (sloped in the x and y directions). The angle that a side 67of an irregularity 38 forms relative to the z-direction has beendesignated as a_(i) in FIG. 21. It is to be understood, however, in thecase of an irregularity 38 which has curved or irregular sides, theangle a_(i) will depend on the reference points used to measure theangle a_(i) formed by the side 67 of the irregularity 38.

Further, each irregularity 38 can have various numbers of differentsides 67. The number of sides 67 can vary depending on the shape of theirregularity 38. For dome-shaped or knob-shaped irregularities, theside(s) 67 of the irregularity 38 will appear as one continuous curvedline when viewed in cross-section. In cases where the irregularity 38has a more complex geometry, there can be a virtually an infinite numberof sides 67 of various cross-sections.

FIG. 21 shows the previously-described coterminous sides 67a of theirregularities 38 which are formed by the interior walls 66a of thepassageways 37. As shown in FIG. 21, these coterminous sides 67a willoften be relatively unequal in length because the coterminous sides 67afor a given irregularity 38 may be formed by the side walls 66a of twoor more radically differently-shaped passageways 37.

FIG. 21 also shows that one or more of the sides 67 of theirregularities 38 may not be formed by the same structure that forms thewalls of neighboring passageways 37. These sides will be referred to asthe independently-formed sides of the irregularities 38, and aredesignated 67b in the drawings. Oftentimes, these independently-formedsides 67b of the irregularities 38 will comprise a portion of the wearsurface on the backside 12 of the belt 10.

In addition, as in the case of the passageways 37, although theirregularities 38 are generally extremely minute, they also have afinite height h_(i), width w_(i), spacing s_(i), and cross-sectionalarea A_(xi). As shown in FIG. 21, the boundaries of the irregularities38 are frequently established by the coterminous sides 67 of theirregularities 38. Since the coterminous sides 67a of an irregularity 38can be quite unequal, the precise height, and also the width, andcross-sectional area A_(xi) of an irregularity 38 may be difficult toexpress.

For the purposes of definition of these characteristics of theirregularities 38, an arbitrary, but uniform reference point will bechosen for taking these measurements. This reference point has beendesignated 110 in FIG. 21. The reference point 110 is a point which lieson the shortest of the coterminous sides 67a of the irregularity 38.More specifically, it is the point on the shortest of the coterminoussides 67a which is the greatest distance inward from the plane definedby the backside of the belt P_(b). FIG. 21 shows that the point 110 maybe in two different places for neighboring irregularities 38.

As shown in FIG. 21, the height h_(i) of any point on an irregularity 38is the distance, measured in the z-direction, from a plane which passesthrough the reference point 110 for the irregularity 38 in issue to theparticular point of interest on the irregularity 38. As shown in FIG.21, the height h_(i) of different portions of an individual irregularity38 may vary across the width of the irregularity 38. In addition, theheight h_(i) of the various irregularities 38 in the backside network35a can vary from irregularity to irregularity.

The width w_(i) of an irregularity 38 is the distance, measured in theeither the x-direction or the y-direction or in some direction inbetween which lies in the X-Y plane, depending upon the cross-sectiontaken, between two points lying on the opposite sides 67 of theirregularity 38. If the sides 67 are formed by a single curved surface,the width w_(i) of the irregularity is the distance measured in the X-Yplane between two points on opposite sides of the curved surface. Asshown in FIG. 21, the width of a different portions of an individualirregularity 38 may vary depending on the portion of the irregularity 38at which the width is measured. In addition, the width of the variousirregularities 38 in the backside network 35a can vary from irregularityto irregularity.

The cross-sectional area of an irregularity A_(xi) is also representedby a cross-hatched area in FIG. 21. The cross-sectional area of anirregularity A_(xi) is the area measured on a given cross-section, ofthe portion of the irregularity 38 which lies between an imaginary linewhich passes through the reference point 110 and the plane defined bythe backside of the belt P_(b).

The irregularities 38 also have a spacing s_(i) between adjacentirregularities 38. As shown in FIG. 21, the spacing betweenirregularities 38 in a given direction s_(i) is the distance measured inthe X-Y plane between the reference point 109 which lies on thecoterminous side 67 of one irregularity 38 to the reference point 109which lies on the nearest coterminous side 67a of the next irregularity38.

The overall pattern of spacing between the irregularities 38 determinesthe distribution of the irregularities 38. Like the passageways, theirregularities 38 can be distributed in an unlimited number of waysacross the backside network 35a of the framework 32. The distribution ofthe irregularities 38 can be random, uniform, regular, or in someparticular pattern. As used herein, the term "uniform" means that thedensity (or number) of irregularities 38 is approximately the same overan entire surface, even though the irregularities 38 do not form anyparticular pattern. As used herein, the term "regular" means that thespacing between adjacent irregularities s_(i) is approximately the sameacross the entire backside network 35a. In addition, as in the case ofthe passageways 37, the irregularities 38 may be distributed across"generally all" portions of the backside network 35a. When theirregularities 38 are distributed across "generally all" of the backsidenetwork 35a, it is meant that while the irregularities 38 can be foundat virtually any particular place on the backside network 35a, theirregularities 38 do not necessarily cover the entire backside network35a. Examples of the various different distributions of theirregularities 38 are shown in the same figures of the accompanyingdrawings which show the corresponding types of distributions of thepassageways 37.

In addition to having the characteristics described above, theirregularities 38 may also be described as either projections ordepressions in the backside network 35a of the framework 32. As usedherein, if an irregularity 38 is referred to as either a projection oras a depression, the frame of reference being used to describe theirregularity 38 is the plane defined by the machine-facing side of thereinforcing structure P_(k2). Any irregularity 38 which projects outwardfrom this plane in the z-direction is a projection. Any irregularity 38which lies inward in the z-direction from the plane P_(k2), is adepression.

The particular characteristics of the textured backside 12 of thepreferred embodiment of the papermaking belt 10 of the present inventiondepend upon the method used to make the belt 10. When the belt isprovided with a backside texture by exposing the photosensitive resinousmaterial to a light source through the reinforcing structure 33 asdescribed herein, the particular characteristics of the backside texturealso depend on the characteristics of the opaque first portion P₀₁. Theparticular characteristics of a representative belt made with theprocess described herein are shown in the enlarged photographs of FIGS.34A-C, and will be discussed in conjunction with the description of themethod used to make the belt shown in the photographs. There are certaingeneral characteristics, however, which are common to the belts whichare made by the method described herein. These characteristics are bestdescribed with reference to FIGS. 11A and 11B.

Generally, as shown in FIGS. 11A and 11B, the passageways 37 arepositioned predominantly in the first projected area A₁ formed by theprojection of the opaque first portion P₀₁. FIGS. 11A and 11B also showthat the plane defined by the backside of the belt P_(b) and the planedefined by the machine-facing side of the reinforcing structure P_(k2)are the same. In other words, the belt 10 is negatively textured. FIGS.11A and 11B also show that the heights of the passageways 37 extendinward from the plane defined by the machine-facing side of thereinforcing structure P_(k2) to the bottom of the structural components40a which comprise the first portion P₀₁.

It is believed that the problems which developed when using the priorsmooth backsided papermaking belts was at least partially the result ofthe extremely sudden application of vacuum pressure which was impartedto the paper web when the paper web was carried by the prior belt overthe vacuum dewatering machinery employed in the papermaking process. Itis believed that the prior smooth backsided papermaking belts wouldactually temporarily create a seal over these vacuum sources. Then, whenthe deflection conduits of the papermaking belt of the prior type wereencountered, the vacuum pressure would be applied in an extremely suddenfashion to the fibrous web situated on top of the resin framework. Thissudden application of vacuum pressure is believed to have caused asudden deflection of the very mobile fibers in the fibrous belt whichwas sufficient to allow these mobile fibers to pass completely throughthe papermaking belt. The difference between the deflection of fibers inthe fibrous web when carried by a prior belt 10a and by the papermakingbelt 10 of the present invention is illustrated schematically in FIGS.23A and 23B and graphically in FIG. 24.

FIG. 23A is a representation of what was believed to occur when theprior papermaking belts 10a encountered the vacuum dewatering equipmentemployed in the papermaking process, such as vacuum box 24. FIG. 23B isa representation of what is believed to occur when the improvedpapermaking belt 10 of the present invention encounters such a vacuumbox 24. FIG. 24 is a graphical representation of the vacuum pressure(differential pressure) which is applied to the fibers in the embryonicweb 18 as the papermaking belts shown in FIGS. 23A and 23B move acrossthe vacuum slot of the vacuum box.

While each of the papermaking belts 10a and 10, respectively shown inFIGS. 23A and 23B comprises a framework 32, having a first surface 34, asecond surface 35, and a reinforcing structure 33, the belts differ inthat the backside network 35a in the second surface 35 of the framework32 of belt 10 is textured whereas the backside network 35a of theframework 32 of belt 10a is smooth. It should be understood, however,that there are numerous other differences between the papermaking belt10 of the present invention and the prior belts (including, but notlimited to the shape of the conduits and the particular type ofreinforcing structure used) which are not shown in FIGS. 23A and 23B.The purpose of FIGS. 23A and 23B is to show the differences in operationof the belts which results from the differences in their backsides. Forsimplicity and clarity, the other differences have been omitted fromFIGS. 23A and 23B.

As shown in FIGS. 23A and 23B, both belts 10a and 10 carry an embryonicweb 18 (having individual fibers designated 18a) on the first surface 34of their respective frameworks 32. In the figures shown, a portion ofeach belt 10a and 10 passes over a single slot 24d of a vacuum box 24.The portion of the vacuum boxes shown also include a leading surface,vacuum box surface 24c₁, which is first encountered when the papermakingbelts travel in the machine direction (from left to right in thefigures) in the papermaking process, and a trailing surface, vacuum boxsurface 24c₂, which is the surface of the vacuum box 24 which isencountered after the papermaking belts pass over the vacuum slot 24d.In addition, at each of the surfaces 24c₁ and 24c₂, adjacent the top ofthe vacuum slot 24d, is a lip, such as leading vacuum box surface lip24b₁ and trailing vacuum box surface lip 24b₂. A vacuum V is appliedfrom a vacuum source (not shown), which exerts pressure on the belts andthe embryonic webs 18 in the direction of the arrows shown. The vacuum Vremoves some of the water from the embryonic web 18 and deflects andrearranges the fibers 18a of the embryonic web into the conduits 36 ofthe framework 32.

In FIG. 23A, because of the smooth nature of the backside network 35a ofthe framework 32, it is believed that a vacuum seal is created betweenthe second surface 35 of the framework 32 and the leading surface 24c₁of the vacuum box 24 at the place designated with reference letter S.When the belt 10a travels to the right, the vacuum slot 24d isencountered, the seal is suddenly broken, and the vacuum pressure V issuddenly applied to the embryonic web 18. This causes a suddendeflection of the fibers 18a in the embryonic web 18 into the conduits36, and some of the more mobile fibers, designated 18a', to passentirely through the belt 10a and accumulate on the trailing lip 24b₁ ofthe vacuum box 24. It has been found that these fibers 18a' willeventually accumulate until they build up into clumps of fibers on thetrailing surface 24c₂ of the vacuum box, creating ridges for papermakingbelt 10a to travel over.

In FIG. 23B, on the other hand, since the backside 12 (particularly thebackside network 35a of the framework 32) of the belt 10 is textured,there are passageways 37 through which air can enter between thebackside surface 12 of the papermaking belt 10 and the leading surface24c₁ of the vacuum box 24 to eliminate the seal between backside network35a of the framework 32 and the leading surface 24c₁ of the vacuum box24. This entry of air is shown schematically by the large arrows V_(L).As shown in FIG. 23B, the entry of air V_(L) permits a more incrementaldeflection of the fiber 18a in the embryonic web 18. Few if any fiberspass through the papermaking belt 10 to accumulate on the trailingvacuum box lip 24b₂. In addition, it is believed that the texturedbackside network 35a of the papermaking belt 10 shown in FIG. 23B mayalso serve a scrubbing or cleaning function to remove any such fiberswhich accumulate on the trailing vacuum box lip 24b₂.

2. Process for Making the Papermaking Belt

As indicated above, the papermaking belt 10 can take a variety of forms.While the method of construction of the papermaking belt 10 isimmaterial so long as it has the characteristics mentioned above,certain methods have been discovered to be useful. By way of background,a detailed description of the process of making the "deflection member"(or "foraminous member") which does not have the improvements disclosedherein is set forth in U.S. Pat. No. 4,514,345, entitled "Method ofMaking a Foraminous Member" which issued to Johnson, et al on Apr. 30,1985. The Johnson, et al. patent is incorporated by reference herein tothe extent it is consistent with the present description. One processfor making the improved papermaking belt 10 of the present invention andseveral variations of the same, is described below.

A preferred embodiment of an apparatus which can be used to construct apapermaking belt 10 of the present invention in the form of an endlessbelt is shown in schematic outline in FIG. 25. In order to show anoverall view of the entire apparatus for constructing a papermaking beltin accordance with the present invention, FIG. 25 was simplified to acertain extent with respect to some of the details of the process. Thedetails of this apparatus, and particularly the manner in which thepassageways 37 and the surface texture irregularities 38 are imparted tothe backside network 35a of the second surface 35 of the framework 32are shown in the figures which follow. It should be noted at this pointthat the scale of certain elements shown may be somewhat exaggerated inthe following drawing figures.

The overall process shown in FIG. 25 generally involves coating areinforcing structure 33 with a liquid photosensitive polymeric resin 70when the reinforcing structure 33 is traveling over a forming unit ortable 71 (or "casting surface") 72. As shown in FIG. 25 and in thefigures which follow, the resin, or "the coating" 70 is applied to atleast one (and preferably both) sides(s) of the reinforcing structure 33so the coating 70 substantially fills the void areas of the reinforcingstructure 33 and forms a first surface 34' and a second surface 35'. Thecoating 70 is distributed so that at least a portion of the secondsurface 35' of the coating is positioned adjacent the working surface 72of the forming unit 71. The coating 70 is also distributed so that thepaper-facing side 51 of the reinforcing structure 33 is positionedbetween the first and second surfaces 34' and 35' of the coating 70. Inaddition, as shown in FIG. 27, the coating 70 is distributed so portionsof the second surface 35' of the coating are positioned between theopaque first portion P.sub. 01 of the reinforcing component 40 and theworking surface 72 of the forming unit 71. The portion of the coatingwhich is positioned between the first surface 34' of the coating and thepaper-facing side 51 of the reinforcing structure 33 forms a resinousoverburden t₀ '. The thickness of the overburden t₀ ' is controlled to apreselected value. The liquid photosensitive resin 70 is then exposed toa light having an activating wavelength (light which will cure thephotosensitive liquid resin) from a light source 73 through a mask 74which has opaque regions 74a and transparent regions 74b and through thereinforcing structure 33. The portions of the resin which have beenshielded or protected from light by the opaque regions 74a of the mask74 and by the first portion P₀₁ of the reinforcing structure 33 are notcured by the exposure to the light. The remaining portions of the resin(the unshielded portions, and those portions that the second portion P₀₂of the reinforcing structure 33 permits the curing of) are cured. Theuncured resin is then removed to leave conduits 36 which pass throughthe cured resin framework 32, and passageways 37 that provide surfacetexture irregularities 38 in the backside network 35a which correspondto those portions of the second surface 35' of the coating 70 which wereprevented from curing by the first portion P₀₁ of the reinforcingstructure 33.

For convenience, the stages in the overall process are broken down intoa series of steps and examined in greater detail in the discussion whichfollows. It is to be understood, however, that the steps described beloware intended to assist the reader in understanding the method of makingthe papermaking belt of the present invention, and that the methoddescribed below is not limited to only a certain number or arrangementof steps. In this regard, it is noted that it is possible to combinesome of the following steps so that they are performed concurrently.Likewise, it is possible to separate some of the following steps intotwo or more steps without departing from the scope of the presentinvention.

First Step

The first step of the process of the present invention is providing aforming unit 71 with a working surface 72.

The forming unit 71 shown in FIG. 25 has working surface which isdesignated 72. In FIG. 25, the forming unit 71 appears as a circularelement which is preferably a drum. The diameter of the drum and itslength are selected for convenience. Its diameter should be great enoughso that the barrier film 76 and the reinforcing structure 33 are notunduly curved during the process. It must also be large enough indiameter so there is sufficient distance of travel about its surface sothat the necessary steps can be accomplished as the drum is rotating.The length of the drum is selected according to the width of thepapermaking belt 10 being constructed. The forming unit 71 is rotated bya conventional drive means which is not illustrated.

FIG. 27 is an enlarged schematic view of one alternative version of thecasting process shown in FIG. 25. FIG. 27 also first illustrates that inthe preferred embodiment of the present process, a hard rubber cover 91,preferably approximately one inch (2.54 cm) thick, is placed over theforming unit 71.

Preferably, the forming unit 71 is covered by a barrier film 76 whichprevents the working surface 72 from being contaminated with resin. Thebarrier film 76 also facilitates the removal of the partially completedpapermaking belt 10' from the forming unit 71. Generally, the barrierfilm 76 can be any flexible, smooth, planar material. The barrier film76 can be made from polypropylene, polyethylene, or polyester sheeting.Preferably, the barrier film is made from polypropylene and is fromabout 0.01 to about 0.1 millimeter (mm) thick. Preferably, the barrierfilm 76 also either absorbs light of the activating wavelength, or issufficiently transparent to transmit such light to the working surface72 of the forming unit 71, and the working surface 12 absorbs the light.The barrier film 76 is also typically chemically treated to prevent theresin from adhering to its surface and also to ensure that the resinspreads evenly across its surface. Preferably, this chemical treatmentis a corona treatment. The corona treatment used in the preparation ofthe barrier film 76 involves apply an electrical discharge to thebarrier film 76 prior to its installation in the apparatus shown in FIG.25.

As shown in FIG. 25, the barrier film 76 is introduced into the systemfrom the barrier film supply roll 77 by unwinding it and causing it totravel in the direction indicated by directional arrow D2. Afterunwinding, the barrier film 76 contacts the working surface 72 offorming unit 71 and is temporarily constrained against the workingsurface 72 by the means discussed below. The barrier film 76 travelswith the forming unit 71 as the forming unit 71 rotates. The barrierfilm 76 is eventually separated from the working surface 72 of theforming unit 71 and travels to the barrier film take-up roll 78 to whereit is rewound. In the embodiment of the process illustrated in FIG. 25,the barrier film 76 is designed for a single use after which it isdiscarded. In an alternative arrangement, the barrier film 76 can takethe form of an endless belt which travels about a series of return rollswhere it is cleaned and reused.

Preferably, the forming unit 71 is also provided with a means forinsuring that barrier film 76 is maintained in close contact with itsworking surface 72. The barrier film 76 can be, for example, adhesivelysecured to working surface 72. Alternatively, the barrier film 76 can besecured to the working surface 72 by a vacuum applied through aplurality of closely-spaced, small orifices distributed across theworking surface 72 of the forming unit 71. Preferably, the barrier film76 is held against the working surface 72 by a conventional tensioningmeans which is not shown in FIG. 25.

Second Step

The second step of the process of the present invention is providing areinforcing structure 33, which has certain elements and characteristics(described below), for incorporation into the papermaking belt.

The general elements and characteristics of the reinforcing structure 33are shown in FIG. 27. FIG. 27 shows that the reinforcing structure 33has a paper-facing side 51, a machine-facing side 52 opposite thepaper-facing side 51, interstices 39, and a reinforcing component 40comprised of a plurality of structural components 40a. A first portionP₀₁ of the reinforcing component 40 has a first opacity O₁ and a secondportion P₀₂ of the reinforcing component 40 has a second opacity O₂ lessthan the first opacity O₁. The first opacity O₁ is sufficient tosubstantially prevent curing of the photosensitive resinous materialwhen the photosensitive resinous material is in its uncured state andthe first portion is positioned between the photosensitive resinousmaterial and an actinic light source 73. The second opacity O₂ issufficient to permit curing of the photosensitive resinous material. Thefirst portion P₀₁ defines a first projected area A₁, a portion of whichis shown in FIG. 27.

As noted above, the reinforcing structure 33 is the element about whichthe papermaking belt 10 is constructed. Any reinforcing structuredisclosed in the preceding section of this specification can be used.Preferably, the reinforcing structure 33 is the woven, multilayer fabricshown in FIGS. 6-11 which is characterized by warp yarns which arevertically stacked directly on top of one another, and the first portionP₀₁ comprises at least some of the warp yarns 53 in the second warplayer D.

Since the preferred papermaking belt 10 is in the form of an endlessbelt, the reinforcing structure 33 should also be an endless belt sincethe papermaking belt 10 is constructed around the reinforcing structure33. As illustrated in FIG. 25, the reinforcing structure 33 which hasbeen provided is arranged so that it travels in the direction indicatedby directional arrow D1 about return roll 78a up, over, and around theforming unit 71 and around return rolls 78b and 78c. It is to beunderstood that in the apparatus used to make the papermaking belt ofthe present invention, there are conventional guide rolls, return rolls,drive means, support rolls and the like which are not shown in FIG. 25.

Third Step

The third step in the process of the present invention is bringing atleast a portion of the machine-facing side 52 of the reinforcingstructure 33 into contact with the working surface 72 of the formingunit 71 (or more particularly in the case of the embodiment illustrated,traveling the reinforcing structure 33 over the working surface 72 ofthe forming unit 71).

As noted above, preferably a barrier film 76 is used to keep the workingsurface 72 of the forming unit 71 free of resin 70. In this case, thethird step will involve bringing at least a portion of themachine-facing side 52 of the reinforcing structure 33 into contact withthe barrier film 76 in such a way that the barrier film 76 is interposedbetween the reinforcing structure 33 and the forming unit 72.

The exact manner in which the reinforcing structure 33 is positionedrelative to either the working surface 72 of the forming unit 71 or thebarrier film 76 depends upon the specific design desired for thepapermaking belt 10. The reinforcing structure 33 can be placed indirect contacting relation with barrier film 76. Alternatively, thereinforcing structure 33 can be spaced some finite distance from barrierfilm 76. Any convenient means can be used to space the reinforcingstructure 33 away from the barrier film 76. For instance the liquidphotosensitive resin 70 could be applied to the machine-facing side 52of the reinforcing structure 33 so that a portion of the coating liesbetween the reinforcing structure 33 and the working surface 72 of theforming unit 71. Preferably, however, at least a portion of themachine-facing side 52 of the reinforcing structure 33 (e.g., themachine side knuckles) is placed directly in contact with the workingsurface 72 of the forming unit 71 (or the barrier film 76 if one isused). The other portions of the reinforcing structure 33, such asraised portions 120, will be spaced away from the working surface 72 ofthe forming unit 71.

Fourth Step

The fourth step in the process is applying a coating of liquidphotosensitive resin 70 to at least one side of the reinforcingstructure 33.

Generally, the coating 70 is applied so that the coating 10substantially fills the void areas 39a of the reinforcing structure 33(the void areas are defined below). The coating 70 is also applied sothat it forms a first surface 34' and a second surface 35'. The coating70 is distributed so that at least a portion of the second surface 35'of the coating 70 is positioned adjacent the working surface 72 of theforming unit 71. The coating 70 is distributed so that the paper-facingside 51 of the reinforcing structure 33 is positioned between the firstand second surfaces 34' and 35' of the coating 70. The portion of thecoating which is positioned between the first surface 34' of the coatingand the paper-facing side 51 of the reinforcing structure 33 forms aresinous overburden t₀ '. The coating 70 is also distributed so thatportions of the second surface 35' of the coating 70 are positionedbetween the first portion P₀₁ of the reinforcing component 40 and theworking surface 72 of the forming unit 71.

For coating the reinforcing structure 33, suitable photosensitive resinscan be readily selected from the many available commercially. Resinswhich can be used are materials, usually polymers, which cure orcross-link under the influence of radiation, usually ultraviolet (UV)light. References containing more information about liquidphotosensitive resins include Green et al., "Photocross-linkable ResinSystems", J. Macro-Sci. Revs. Macro Chem. C21 (2), 187-273 (1981-82);Bayer, "A Review of Ultraviolet Curing Technology", Tappi PaperSynthetics Conf. Proc., Sept. 25-27, 1978, pp. 167-172; and Schmidle,"Ultraviolet Curable Flexible Coatings", J. of Coated Fabrics, 8, 10-20(July, 1978). All the preceding three references are incorporated hereinby reference. Especially preferred liquid photosensitive resins areincluded in the Merigraph series of resins made by HerculesIncorporated, Wilmington, Del. A most preferred resin is Merigraph resinEPD 1616.

In the preferred process of carrying out the present invention,antioxidants are added to the resin to protect the finished papermakingbelt 10 from oxidation and increase the life of the papermaking belt.Any suitable antioxidants can be added to the resin. The preferredantioxidants are Cyanox 1790, which is available from American Cyanamidof Wayne, N.J. 07470, and Iraganox 1010, which is made by Ciba Geigy ofArdsley, N.Y. 10502. In the preferred process for making the papermakingbelt 10 of the present invention, both antioxidants are added to theresin. The antioxidants are added in the following respective amounts,Cyanox 1790 1/10 of 1%, and Iraganox 1010 8/10 of 1%. Both antioxidantsare added so the papermaking belt 10 of the present invention isprotected from several different species of oxidizing agents.

Any technique by which the liquid material can be applied to thereinforcing structure 33 is suitable for applying the coating 70. Asshown in FIG. 25, in the preferred method of carrying out the presentinvention, the liquid photosensitive resin 70 is applied to thereinforcing structure 33 at two stages. The first stage occurs at theplace indicated by extrusion header 79. The first stage is referred toas the "prefill" stage because it takes place before the portion of thereinforcing structure 33 being coated is brought into contact with theworking surface 72 of the forming unit 71. At the first stage, a firstcoating of liquid photosensitive resin is applied to at least themachine-facing side 52 of the reinforcing structure 33 by the extrusionheader 79 to at least partially fill the void areas 39a of thereinforcing structure 33. Preferably, the first coating substantiallyfills the void areas 39a of the reinforcing structure 33. The void areasare shown best in FIG. 22D. As used herein, the term "void areas" (or"void volume") refers to all of the open spaces of the reinforcingstructure 33 which lie between the plane defined by the paper-facingside of the reinforcing structure P_(k1) and the plane defined by themachine-facing side of the reinforcing structure P_(k2) (that is, thosespaces between the two planes not occupied by the reinforcing component40). The void areas 39a thus comprise the interstices 39 and any otheropen spaces which lie between the planes P_(k1) and P_(k2).

The application of resin 70 by the extrusion header 79 is employed inconjunction with the application of a second coating of liquidphotosensitive resin 70 at a second stage by a nozzle 80 locatedadjacent to the place where the mask 74 is introduced into the system.The nozzle 80 applies the second coating of liquid photosensitive resin70 to the paper-facing side 51 of the reinforcing structure 33. It isnecessary that liquid photosensitive resin 70 be evenly applied acrossthe width of reinforcing structure 33 and that the requisite quantity ofmaterial be worked through interstices 39 to substantially fill the voidareas 39a of the reinforcing structure 33. The second coating is appliedso that the first coating together with the second coating forms asingle coating, coating 70, which has the first surface 34' and thesecond surface 35' described above and is distributed as describedabove. Thus, the single coating 70 is distributed so that: at least aportion of the second surface 35' of the coating is positioned adjacentthe working surface 72 of the forming unit 71; the paper-facing side 51of the reinforcing structure 33 is positioned between the first andsecond surfaces 34' and 35' of the coating 70, and the portion of thecoating which is positioned between the first surface 34' and thepaper-facing side 51 of the reinforcing structure 33 forms a resinousoverburden t₀ '.

In the drawings, it is thus seen that the stages at which the liquidphotosensitive resin 70 is applied to the reinforcing structure 33 donot necessarily always occur in time sequence immediately after thethird step set forth above. That is, the (first stage of the) coatingstep occurs before, not after, the machine-facing side 52 of thereinforcing structure 33 is brought into contact with the workingsurface 72 of the forming unit 71 if one is looking at a particularportion of the reinforcing structure 33 which is traveling around thereinforcing structure return roll 78a toward the forming unit 71. On theother hand, if one is looking at the overall process of assembling theapparatus shown in FIG. 25, it is apparent that at least a portion ofthe endless belt which comprises the reinforcing structure 33 wouldgenerally be placed in contact with the working surface 72 of theforming unit 71 before any coating of the reinforcing structure 33 takesplace. As described herein, however, the process is generally examinedfrom the former perspective.

In the embodiment shown in the drawings, the second stage of applyingthe photosensitive resin (or "post-fill stage") occurs after the placewhere the reinforcing structure 33 first comes in contact with theforming unit 71 when it is traveling around the reinforcing structurereturn rollers. It is to be understood that these two events (that is,applying the coating and bringing the reinforcing structure 33 intocontact with the working surface 72 of the forming unit 71) couldinstead occur simultaneously, or that the photosensitive resin could beapplied to the top surface (that is, the paper-facing side 51) of thereinforcing structure before the point where the reinforcing structure33 is first placed in contact with the forming unit 71. The process ofthe present invention is intended to include all possible arrangementsand sequences of the basic steps described herein. Preferably, however,the coating of the reinforcing structure 33 takes place in the ordershown in the drawings.

Fifth Step

The fifth step in the process of this invention is controlling thethickness of the overburden t₀ ' of the resin coating 70 to apreselected value. In the preferred embodiment of the belt makingapparatus shown in the drawings, this step takes place at approximatelythe same time, i.e., simultaneously, with the second stage of applying acoating of liquid photosensitive resin to the reinforcing structure 33.

The preselected value of the thickness of the overburden corresponds tothe thickness desired for the papermaking belt 10. This thickness, alsonaturally, follows from the expected use of the papermaking belt. Whenthe papermaking belt 10 is to be used in the papermaking processdescribed hereinafter, it is preferred that the thickness, t, of thepapermaking belt 10 be from about 0.01 mm to about 3.0 mm. Otherapplications, of course, can require thicker papermaking belts which canbe 3 centimeters thick or thicker.

Any suitable means for controlling the thickness can be used. The meansused for controlling the thickness of the overburden illustrated in FIG.25 is the use of nip roll 81, which also serves as a mask guide roll.The clearance between the nip roll 81 and the forming unit 71 can becontrolled mechanically by any conventional means which are not shown.The nip roll 81, in conjunction with the mask 74 and the mask guide roll82, tends to smooth the surface of liquid photosensitive resin 70 and tocontrol its thickness.

Sixth Step

The sixth step in the process of this invention can be considered aseither a single step or as two separate steps which comprise: (1)providing a mask 74 having opaque 74a and transparent regions 74b inwhich the opaque regions 74a together with the transparent regions 74bdefine a preselected pattern in the mask; and (2) positioning the mask74 between the coating of liquid photosensitive resin 70 and an actiniclight source 73 so that the mask 74 is in contacting relation with thefirst surface 34' of the coating of liquid photosensitive resin 70.

The mask 74 can, alternatively, be positioned so that it is positioned afinite distance away from the first surface 34' of the coating 70.Preferably, however, for the reasons described below, it is in contactwith the first surface 34' of the coating 70.

The purpose of the mask 74 is to protect or shield certain areas of theliquid photosensitive resin 70 from exposure to light from the actiniclight source. Naturally, if certain areas are shielded, it follows thatcertain areas are not shielded and that liquid photosensitive resin 70in those unshielded areas will be exposed later to activating light andwill be cured. After the steps described herein are performed, theshielded regions will normally comprise the preselected pattern formedby the conduits 36 in the hardened resin framework 32.

The mask 74 can be made from any suitable material which can be providedwith opaque regions 74a and transparent regions 74b. A material in thenature of a flexible photographic film is suitable for use as a mask 74.The flexible film can be polyester, polyethylene, or cellulosic or anyother suitable material. The opaque regions 74a should be opaque tolight which will cure the photosensitive liquid resin. For the preferredliquid photosensitive resin used herein, the opaque regions 74a shouldbe opaque to light having a wavelength of between about 200 and about400 nanometers. The opaque regions 74a can be applied to mask 74 by anyconvenient means such as by a blue printing (or ozalid processes), or byphotographic or gravure processes, flexographic processes, or rotaryscreen printing processes. Preferably, the opaque regions 74b areapplied to the mask by a blueprinting (on ozalid) process.

The mask 74 can be an endless loop (the details of which areconventional, and are, therefore, not shown) or it can be supplied fromone supply roll transverse through the system to a takeup roll, neitherof which is shown in the illustration since they are also conventional.The mask 74 travels in the direction indicated by directional arrow D3,turns under nip roll 81 where it is brought into contact with thesurface of liquid photosensitive resin 70, and then travels to maskguide roll 82 in the vicinity of which it is removed from contact withthe resin 70. In this particular embodiment, the control of thethickness of the resin 70 and the positioning of the mask 74 occursimultaneously.

Seventh Step

The seventh step of the process of this invention comprises curing theunshielded portions of liquid photosensitive resin in those regions leftunprotected by the transparent regions 74b of the mask 74 and curingthose portions of the coating 70 that the second portion P₀₂ of thereinforcing structure 33 permits the curing of, and leaving the shieldedportions and those portions of the coating positioned between the firstportion P₀₁ of the reinforcing structure 33 and the working surface 72of the forming unit 71 uncured by exposing the coating of liquidphotosensitive resin 70 to light of an activating wavelength from thelight source 73 through the mask 74 to form a partially-formed compositebelt 10'.

In the embodiment illustrated in FIG. 25, the barrier film 76, thereinforcing structure 33, the liquid photosensitive resin 70, and themask 74 all form a unit which travels together from nip roll 81 to thevicinity of mask guide roll 82. Intermediate the nip roll 81 and themask guide roll 82 and positioned at a location where the barrier film76 and the reinforcing structure 33 are still adjacent the forming unit71, the liquid photosensitive resin 70 is exposed to light of anactivating wavelength which is supplied by an exposure lamp 73.

The exposure lamp 73, in general, is selected to provide illuminationprimarily within the wavelength which causes curing of the liquidphotosensitive resin 70. That wavelength is a characteristic of theliquid photosensitive resin 70. Any suitable source of illumination,such as mercury arc, pulsed xenon, electrodeless, and fluorescent lamps,can be used. As described above, when the liquid photosensitive resin 70is exposed to light of the appropriate wavelength, curing is induced inthe exposed portions of the resin 70. Curing is generally manifested bya solidification of the resin in the exposed areas. Conversely, theunexposed regions remain fluid.

The intensity of the illumination and its duration depend upon thedegree of curing required in the exposed areas. The absolute values ofthe exposure intensity and time depend upon the chemical nature of theresin, its photo characteristics, the thickness of the resin coating,and the pattern selected. For the preferred resin, Merigraph resin EPD1616, this amount ranges from approximately 100 to approximately 1,000millijoules/cm², with the preferred range being between approximately300 and approximately 800 millijoules/cm², and the most preferred rangebeing between approximately 500 and approximately 800 millijoules/cm².

The intensity of the exposure and the angle of incidence of the lightcan have an important effect on the presence or absence of taper in thewalls 44 of the conduits 36. In addition to having an effect on thetapering of the walls 44 of the conduits 36, the intensity of theexposure and the angle of incidence of the light will affect thepermeability of the hardened framework 32 to air. This permeability toair ("air permeability") is of importance to the use of the papermakingbelt of the present invention in blow-through drying papermakingprocesses. It is apparent that if there is a high degree of collimationof the light of the activating wavelength, the walls 44 of the conduits36 will be less tapered. Less tapered (or more nearly vertical) conduitwalls will provide the papermaking belt with a higher air permeabilitythan inwardly tapered walls (for a given first surface knuckle area)because the total area of the papermaking belt through which the air canflow is greater when the walls 44 of the conduits 36 are not taperedinwardly.

In the preferred embodiment of the present invention, the angle ofincidence of the light is collimated to better cure the photosensitiveresin in the desired areas, and to obtain the desired angle of taper inthe walls 44 of the finished papermaking belt. Other means ofcontrolling the direction and intensity of the curing radiation, includemeans which employ refractive devices (i.e., lenses), and reflectivedevices (i.e., mirrors). The preferred embodiment of the presentinvention employs a subtractive collimator (i.e., an angulardistribution filter or a collimator which filters or blocks UV lightrays in directions other than those desired). Any suitable device can beused as a subtractive collimator. A dark colored, preferably black,metal device formed in the shape of a series of channels through whichlight directed in the desired direction may pass is preferred. In thepreferred embodiment of the present invention, the collimator is of suchdimensions that it transmits light so the resin network when cured has aprojected surface area of 35% on the topside of the papermaking belt,and 65% on the backside.

Eighth Step

The eighth step in the process in the present invention is removingsubstantially all of the uncured liquid photosensitive resin from thepartially-formed composite belt 10' to leave a hardened resin framework32 around at least a portion of the reinforcing structure 33.

In this step, the resin which has been shielded from exposure to lightis removed from the partially-formed composite belt 10' in the mannerdescribed below to provide the framework 32 with a plurality of conduits36 in those regions which were shielded from the light rays by theopaque regions 74a of the mask 74 and passageways 37 that providesurface texture irregularities 38 in the backside network 35b of theframework 32 which correspond to the portions of the second surface 35'of the coating which were prevented from curing by the first portion P₀₁of the reinforcing structure 33.

In the embodiment shown in FIG. 25, at a point in the vicinity of themask guide roll 82, the mask 74 and the barrier film 76 are physicallyseparated from the partially-formed composite belt 10' which comprisesthe reinforcing structure 33 and the now partly-cured resin 70, alongwith a certain amount of uncured resin. The composite of the reinforcingstructure 33 and the partly cured resin 70 travels to the vicinity ofthe first resin removal shoe 83a. A vacuum is applied to one side of thecomposite belt 10' at the first resin removal shoe 83a so that asubstantial quantity of the uncured liquid photosensitive resin isremoved from the composite belt 10'.

As the composite belt 10' travels farther, it is brought into thevicinity of resin wash shower 84 and resin wash station drain 85 atwhich point the composite belt 10' is thoroughly washed with water orother suitable liquid to remove essentially all of the remaining uncuredliquid photosensitive resin which is discharged from the system throughresin wash station drain 85. At the second resin removal shoe 83b, anyresidual wash liquid and uncured liquid resin is removed from thecomposite belt 10' by the application of vacuum. At this point, thecomposite belt 10' now comprises the reinforcing structure 33 and theassociated hardened resin framework 32 and represents the papermakingbelt 10 which is the product of this process.

Optionally, and preferably, as shown in FIG. 25, there can be a secondexposure of the resin to activating light (hereinafter sometimesreferred to as the "post-cure step") so as to complete the curing of theresin and to increase the hardness and durability of the cured resinframework 32. The post-cure step takes place at the place designated bythe reference to the following FIG. 26. FIG. 26 is an enlarged schematicrepresentation of this post-cure step.

As shown in FIG. 26, the composite belt 10' is subjected to a secondexposure of light of the activating wavelength by post cure UV lightsource 73a. This second exposure, however, takes place when thecomposite belt 10' is submerged under water 86. In order to submerge thecomposite belt 10', as shown in FIG. 26, the composite belt 10' isdiverted somewhat from the path it had been traveling along by rollers87a, 87b, 87c, and 87d into the water 86 provided by water bath 88. Ithas been found that it is important that the composite belt 10' besubmerged for this post-cure exposure; otherwise, the finished belt 10will be inordinately sticky or tacky. In addition, it has also beenfound necessary to add Sodium Sulfite (Na₂ SO₃) to remove as much of thedissolved Oxygen from the water as possible to aid in the completepolymerization of the resin. Sodium Sulfite is added in the approximateamount of 2 percent or less by weight of the water in the post cure bath88.

In addition, FIG. 26 shows that a mirror 89 is placed on the bottomsurface 90 of the water bath 88 in this post-cure process. The mirror 89serves to reflect the UV light which reaches the mirror 89 back onto theunderside or backside 12 of the composite belt 10'. This step isparticularly important in fully curing the portion of the resin whichforms the passageways and irregularities in the backside network 35a ofthe second surface 35 of the framework 32 of the finished papermakingbelt 10. As shown in the preceding figure, all of the UV light has beensupplied from sources located above the top side of the composite belt10'. The amount of UV light which is supplied during this post-cureprocess, again is dependent upon the particular resin involved, as wellas the depth and pattern of curing desired. For the preferred resin,Merigraph resin EPD 1616, the dosages specified above for the precurestep are also suitable for the post-cure step. It is not necessary,however, to collimate the light in the post-cure stage because theconduits or channels have already been suitably formed in the framework.

The process continues until such time as the entire length ofreinforcing structure 33 has been treated and converted into thepapermaking belt 10.

Should it be desired to construct a papermaking belt having differentpatterns superimposed one on another or having patterns of differentthicknesses, the reinforcing structure can be subjected to multiplepasses through the process. Multiple passes through the process of thisinvention can also be used to construct papermaking belts of relativelygreat thickness.

3. The Papermaking Process

The papermaking process which utilizes the improved papermaking belt 10of the present invention is described below, although it is contemplatedthat other processes may also be used to make the paper productsdescribed herein. By way of background, a process for making paper whichdoes not include the improvements of the present process or utilize theimproved papermaking belt 10 of the present invention is set out indetail in U.S. Pat. No. 4,529,480, entitled "Tissue Paper" which issuedto Paul D. Trokhan on Jul. 16, 1985. The Trokhan patent is incorporatedby reference herein to the extent it is consistent with thisdescription. The improvements to the process described in the Trokhanpatent are provided below.

The overall papermaking process which uses the papermaking belt of thepresent invention comprises a number of steps or operations which occurin the general time sequence as noted below. In the followingparagraphs, each step will be discussed in detail in reference toFIG. 1. It is to be understood, however, that the steps described beloware intended to assist the reader in understanding the process of thepresent invention, and that the invention is not limited to processeswith only a certain number or arrangement of steps. In this regard, itis noted that it is possible to combine the following steps so that theyare performed concurrently. Likewise, it is possible to separate thefollowing steps into two or more steps without departing from the scopeof this invention.

FIG. 1 is a simplified, schematic representation of one embodiment of acontinuous papermaking machine useful in the practice of the papermakingprocess of the present invention. The papermaking belt 10 of the presentinvention is shown in the form of an endless belt. The particularpapermaking machine illustrated in FIG. 1 is a Fourdrinier wire machinewhich is generally similar in configuration and in the arrangement ofits belts to the papermaking machine disclosed in U.S. Pat. No.3,301,746, issued to Sanford and Sisson on Jan. 31, 1967, which isincorporated by reference herein.

It is also contemplated that the twin wire papermaking machineillustrated in FIG. 1 of U.S. Pat. No. 4,102,737, issued to Morton onJul. 25, 1978, which patent is incorporated by reference herein, couldbe used to practice the present invention. If the twin wire papermakingmachine disclosed in U.S. Pat. No. 4,102,737, Morton, is used topractice the present invention, the papermaking belt of the presentinvention would replace the drying/imprinting fabric represented byreference numeral 4 in the drawing figures of the Morton patent. Allremaining references to drawing figures, however, will be to thedrawings which accompany the present specification.

First Step

The first step in the practice of the papermaking process of the presentinvention is the providing of an aqueous dispersion of papermakingfibers 14.

The equipment for preparing the aqueous dispersion of papermaking fibers14 is well-known and is therefore not shown in FIG. 1. The aqueousdispersion of papermaking fibers 14 is provided to a headbox 13. Asingle headbox is shown in FIG. 1. However, it is to be understood thatthere may be multiple headboxes in alternative arrangements of thepapermaking process of the present invention. The headbox(es) and theequipment for preparing the aqueous dispersion of papermaking fibers arepreferably of the type disclosed in U.S. Pat. No. 3,994,771, issued toMorgan and Rich on Nov. 30, 1976, which is incorporated by referenceherein. The preparation of the aqueous dispersion and thecharacteristics of the aqueous dispersion are described in greaterdetail in U.S. Pat. No. 4,529,480 issued to Trokhan on Jul. 16, 1985,which is incorporated herein by reference.

The aqueous dispersion of papermaking fibers 14 supplied by the headbox13 is delivered to a forming belt, such as the Fourdrinier wire 15 forcarrying out the second step of the papermaking process. The Fourdrinierwire 15 is supported by a breast roll 16 and a plurality of return rollsdesignated 17 and 17a. The Fourdrinier wire 15 is propelled in thedirection indicated by directional arrow A by a conventional drive meanswhich is not shown in FIG. 1. There may also be associated with thepapermaking machine shown in FIG. 1 optional auxiliary units and deviceswhich are commonly associated with papermaking machines and withFourdrinier wires, including forming boards, hydrofoils, vacuum boxes,tension rolls, support rolls, wire cleaning showers, and the like, whichare conventional, and are, therefore, also not shown in FIG. 1.

Second Step

The second step in the papermaking process is forming an embryonic web18 of papermaking fibers on a foraminous surface from the aqueousdispersion 14 supplied in the first step. The Fourdrinier wire 15 servesas the foraminous surface in the papermaking machine shown in FIG. 1. Asused herein, the "embryonic web" is the web of fibers which is subjectedto rearrangement on the papermaking belt 10 of the present inventionduring the course of the papermaking process.

The characteristics of the embryonic web 18 and the various possibletechniques for forming the embryonic web 18 are described in U.S. Pat.No. 4,529,480 which is incorporated by reference herein. In the case ofthe process shown in FIG. 1, the embryonic web 18 is formed from theaqueous dispersion of papermaking fibers 14 between breast roll 16 andreturn roll 17 by depositing the aqueous dispersion 14 onto theFourdrinier wire 15, and removing a portion of the aqueous dispersingmedium. Conventional vacuum boxes, forming boards, hydrofoils, and thelike which are not shown in FIG. 1 are useful in effecting the removalof water from the aqueous dispersion 14.

After the embryonic web 18 is formed, it travels with Fourdrinier wire15 about the return roll 17 and is brought into the proximity of asecond papermaking belt, the papermaking belt 10 of the presentinvention.

Third Step

The third step in the papermaking process is contacting (or associating)the embryonic web 18 with the paper-contacting side 11 of thepapermaking belt 10 of the present invention.

The purpose of this third step is to bring the embryonic web 18 intocontact with the paper-contacting side of the papermaking belt 10 onwhich the embryonic web 18, and the individual fibers therein, will besubsequently deflected, rearranged, and further dewatered. The embryonicweb 18 is brought into contact with the papermaking belt 10 of thepresent invention by the Fourdrinier wire 15. The Fourdrinier wire 15brings the embryonic web 18 into contact with, and transfers theembryonic web 18 to the papermaking belt 10 of the present invention inthe vicinity of vacuum pickup shoe 24a.

In the embodiment illustrated in FIG. 1, the papermaking belt 10 of thepresent invention travels in the direction indicated by directionalarrow B. The papermaking belt 10 passes around the papermaking beltreturn rolls 19a and 19b, impression nip roll 20, papermaking beltreturn rolls 19c, 19d, 19e and 19f, and emulsion distributing roll 21(which distributes an emulsion 22 onto the papermaking belt 10 from anemulsion bath 23). The loop that the papermaking belt 10 of the presentinvention travels around also includes a means for applying a fluidpressure differential to the paper web, which in the preferredembodiment of the present invention, comprises vacuum pickup shoe 24aand a vacuum box such as multislot vacuum box 24. Also on the loop is apredryer 26. In addition, in between papermaking belt return rolls 19cand 19d, and also in between papermaking belt return rolls 19d and 19e,are water showers 102 and 102a, respectively. The purpose of the watershowers 102 and 102a is to clean the papermaking belt 10 of any paperfibers, adhesives, and the like, which remain attached to the section ofthe papermaking belt 10 which has traveled through the final step in thepapermaking process. Associated with the papermaking belt 10 of thepresent invention, and also not shown in FIG. 1 are various additionalsupport rolls, return rolls, cleaning means, drive means, and the likecommonly used in papermaking machines and all well known to thoseskilled in the art.

The function of the emulsion distributing roll 21 and emulsion bath 23will be discussed in conjunction with the third step for convenience.The emulsion distributing roll 21 and the emulsion bath 23 continuouslyapply an effective amount of a chemical compound (or compounds) to thebelt 10 during the papermaking process. The chemical compounds can beapplied to the papermaking belt 10 at any point during the papermakingprocess, although it is preferred the chemicals be added to thepaper-contacting side 11 of the belt 10 at a particular point in thebelt's revolution when the belt 10 is not carrying a paper web. Thisnormally will be after (as will be described more fully herein) thepredried paper web 27 has been transferred off the papermaking belt 10to the surface of the Yankee dryer drum 28 and the belt 10 is returningto contact another embryonic web 18 (i.e., in the vicinity of emulsiondistribution roll 21).

The chemical compound or compounds are preferably applied to thepapermaking belt 10 in the form of an emulsion, such as by emulsion 22shown in FIG. 1. These compound(s) serve the dual purpose of: (1) actingas a release agent, or release emulsion (a coating on the papermakingbelt 10 of the present invention so the paper releases from and does notstick to the belt after the steps of the papermaking process have beenperformed on the paper web); and, (2) treating the belt to extend itsuseful life by reducing the tendency of the resinous framework 32 todegrade due to oxidation (that is, the emulsion 22 also serves as anantioxidant). Preferably, the chemical compound(s) are applied uniformlyto the paper-contacting side 11 of the belt 10 so substantially theentire paper-contacting side 11 benefits from the chemical treatment.

The preferred emulsion 22 is primarily comprised of five compounds,although it is contemplated that other or additional suitable compoundscould be used. The preferred composition contains water, a high-speedturbine oil known as "Regal Oil", Dimethyl distearyl ammoniumchloride,cetyl alcohol, and an antioxidant.

As used herein, the term "Regal Oil" refers to the compound which iscomprised of approximately 87% saturated hydrocarbons and approximately12.6% aromatic hydrocarbons with traces of additives, which ismanufactured as product number R & O 68 Code 702 by the Texaco OilCompany of Houston, Tex. The purpose of the Regal Oil in the compositiondescribed above is to provide the emulsion with properties which allowit to act as a release agent.

Dimethyl distearyl ammoniumchloride is sold under the tradename ADOGENTA 100 by the Sherex Chemical Company, Inc., of Rolling Meadows, Ill.Hereinafter, Dimethyl distearyl ammoniumchloride will be referred to asADOGEN for convenience. ADOGEN is used in the emulsion as a surfactantto emulsify or stabilize the oil particles (of the Regal Oil) in thewater. As referred to herein, the term "surfactant" refers to a surfaceactive agent, one end of which is hydrophilic, and the other end ofwhich is hydrophobic, which migrates to the interface between ahydrophilic substance and a hydrophobic substance to stabilize the twosubstances.

As used herein, "cetyl alcohol" refers to a C₁₆ linear fatty alcohol.Cetyl alcohol is manufactured by The Procter & Gamble Company ofCincinnati, Ohio. Cetyl Alcohol, like ADOGEN is used as a surfactant inthe emulsion utilized in the present invention.

As used herein, the term "antioxidant" refers to a compound, which whenapplied to the surface of an article, the surface of which is subject tooxidation, reduces the article's tendency to oxidize (i.e., combine withoxygen). In particular, in this specification, the term "antioxidant"refers to compounds which reduce the tendency of the cured resin networkof the papermaking belt 10 of the present invention to oxidize. Apreferred antioxidant is Cyanox 1790 which can be purchased fromAmerican Cyanamid of Wayne, N.J. 07470.

The relative percentages of the compounds as used in the emulsion, areset out in the following table:

    ______________________________________                                                         Volume   Weight                                              Component        (gal.)   (lbs.)                                              ______________________________________                                        Water            518      4,320.0                                             REGAL OIL         55      421.8                                               ADOGEN           N/A*     24                                                  Cetyl Alcohol    N/A*     16                                                  Cyanox 1790      N/A*     5.8                                                 ______________________________________                                         *N/A  Component is added in solid form                                   

Fourth Step

The fourth step in the papermaking process involves applying a fluidpressure differential of a suitable fluid to the embryonic web 18 with avacuum source to deflect at least a portion of the papermaking fibers inthe embryonic web 18 into the conduits 36 of the papermaking belt 10 andto remove water from the embryonic web 18 through the conduits 36 toform an intermediate web 25 of papermaking fibers. The deflection alsoserves to rearrange the fibers in the embryonic web 18 into the desiredstructure.

The preferred method of applying a fluid pressure differential (or"differential fluid pressure"), as will also be more fully describedherein, is by disposing the embryonic web 18 in such a way that the webis exposed to the vacuum through the conduits 36 by the application ofvacuum from the backside 12 of the papermaking belt 10 of the presentinvention. In FIG. 1, this preferred method is illustrated by the use ofvacuum pickup shoe 24a and the multislot vacuum box 24. Preferably, avacuum pressure of between approximately 8 and 12 inches (20.32 cm and30.48 cm) of mercury is applied at the vacuum pickup shoe 24a and avacuum pressure of between approximately 15 and 20 inches (38.1 cm and50.8 cm) of mercury is applied at the multislot vacuum box 24. In thepreferred embodiment of the present process, therefore, the fluidpressure differential will typically be a negative pressure (i.e., lessthan atmospheric pressure), and the suitable fluid is air.Alternatively, or additionally, positive pressure in the form of air orsteam pressure can be applied through Fourdrinier wire 15 to theembryonic web 18 in the vicinity of pickup shoe 24a or vacuum box 24.The means for applying such a positive pressure are conventional, andare, therefore, not shown in FIG. 1.

The deflection of the fibers into the conduits 36 is illustrated inFIGS. 1A and 1B. FIG. 1A is a simplified representation of across-section of a portion of a papermaking belt 10 and embryonic web 18after the embryonic web 18 has been associated with the papermaking belt10, but before the deflection of the fibers into conduits 36 occurs. Asshown in FIG. 1A, the embryonic web 18 is still in contact with theFourdrinier wire 15 (or more specifically, sandwiched between theFourdrinier wire 15 and the papermaking belt 10 of the presentinvention). In FIG. 1A, only one conduit 36 is shown and the embryonicweb 18 is shown associated with the paper side network surface 34a ofthe framework 32 papermaking belt 10.

The portion of the papermaking belt depicted in FIGS. 1A and 1B has beensimplified by omitting the reinforcing structure which is generally partof the preferred embodiment of the papermaking belt of the presentinvention, and also by showing the walls 44 of the conduits 36 asstraight vertical lines in cross-section, when in the preferredembodiment of the present invention as described above, the profile ofthe walls 44 of the conduits is somewhat more complex. In addition, theopening of conduit 36 in the first surface 34, first conduit opening 42,and its opening in second surface 35, second conduit opening 43 areshown essentially equal in size and shape when in the preferredembodiment of the present invention the openings of the conduits in thesecond surface 35 will be smaller than the openings of the conduits inthe first surface 34 of the framework 32. FIG. 1B, like FIG. 1A, is asimplified cross-sectional view of a portion of the papermaking belt 10.This view, however, illustrates the transformation of the embryonic web18 into intermediate web 25 by the deflection of the fibers of theembryonic web 18 into the conduit 36 under the application of a fluidpressure differential. FIG. 1B shows that a substantial portion of thefibers in embryonic web 18 and, thus, embryonic web 18 itself, has beendisplaced into the conduit 36 below the paper side network surface 34ainto conduit 36 to form the intermediate web 25. Rearrangement of theindividual fibers in embryonic web 18 (the details of which are notshown) occurs during deflection.

FIG 1B also shows that at the point when the fibers in the embryonic web18 have been deflected into the conduit 36 and rearranged, the embryonicweb 18 is no longer in contact with the Fourdrinier wire 15. As shown inFIG. 1, the web 18 becomes separated from the Fourdrinier wire 15immediately after leaving the vicinity of the pickup shoe 24a.

Either at the time the fibers are deflected into the conduits 36 orafter such deflection occurs, water is removed from the embryonic web 18through the conduits 36. Water removal occurs under the action of thefluid pressure differential. It is important, however, that there beessentially no water removal from the embryonic web 18 prior to thedeflection of the fibers into the conduits 36. As an aid in achievingthis condition, at least those portions of the conduits 36 surrounded bythe paper side network 34a, are generally isolated from one another.This isolation, or compartmentalization, of conduits 36 is of importanceto insure that the force causing the deflection, such as an appliedvacuum, is applied relatively suddenly and in a sufficient amount tocause deflection of the fibers. This is to be contrasted with thesituation in which the conduits 36 are not isolated. In this lattersituation, vacuum will encroach from adjacent conduits 36 which willresult in a gradual application of the vacuum and the removal of waterwithout the accompanying deflection of the fibers.

In the machine illustrated in FIG. 1, water removal initially occurs atthe pickup shoe 24a and vacuum box 24. Since the conduits 36 are openthrough the thickness of a papermaking belt 10, water withdrawn from theembryonic web 18 passes through the conduits 36 and out of the system.Water removal continues until the consistency of the web associated withconduits 36 is increased to from about 20% to about 35%.

Fifth Step

The fifth step is traveling the papermaking belt 10 and the embryonicweb 18 over the vacuum source described in the forth step. Preferably,the fifth step will occur while the fourth step is taking place. Thebelt 10 carries the embryonic web 18 on its paper-contacting side 11over the vacuum source. At least a portion of the textured backside 12of the belt 10 is generally in contact with the surface of the vacuumsource as the belt 10 travels over the vacuum source.

The step of traveling the papermaking belt 10 of the present inventionover the vacuum source reduces the undesirable accumulation of paperfibers on the vacuum box lips. While not wishing to be bound by anyparticular theory, it is believed that one of the keys in achieving thisreduction in the process of the present invention is controlling therelative suddenness of the deflection during the preceding step. Thedeflection of the fibers is controlled by using a papermaking belt whichhas a textured backside 12. The textured backside surface allows acertain amount of air to enter across the backside 12 of the papermakingbelt 10 when the backside 12 is in contact with the surfaces of thepickup shoe 24a and the vacuum box 24. The backside network 35a of thebelt 10 has passageways 37 which provide spaces through which at leastsome of the air leakage can enter. This is to be contrasted with theprior deflection member which was provided with bottom surface which wasrelatively planar. The planar surface tended to form a seal on thevacuum box used to deflect the fibers of the embryonic web, resulting inan extremely sudden application of vacuum pressure when the seal wasbroken. Thus, controlling the deflection of the fibers in the embryonicweb 18 may be a step which inherently occurs in conjunction with thefifth step, or it may be considered to be a separate step.

It is also believed that these passageways 37, which provide surfacetexture irregularities 38 in the backside 12 of the papermaking belt 10have a cleaning effect on the lips or surfaces of the vacuum dewateringequipment used in the papermaking process. This cleaning action tends toremove any undesirable accumulation of papermaking fibers on this vacuumequipment. This cleaning action is believed to occur when the vacuumsource has at least one surface that the papermaking belt travels overduring the deflection step. Thus, the cleaning of the surfaces of thevacuum dewatering equipment may be a step which inherently occurs inconjunction with the fifth step, or it may be considered to be aseparate step. If considered as an additional step, this step wouldcomprise contacting the surface of said vacuum source with the texturedbackside 12 of the belt 10 to clean off any papermaking fibers whichhave accumulated on the surface of said vacuum source.

Following the application of the vacuum pressure and the traveling ofthe papermaking belt 10 and the embryonic web 18 over the vacuum source,the embryonic web 18 is in a state in which it has been subjected to afluid pressure differential and deflected but not fully dewatered, thusit is now referred to as the "intermediate web 25."

Sixth Step

The sixth step in the papermaking process is an optional step whichcomprises drying the intermediate web 25 to form a predried web ofpapermaking fibers. Any convenient means conventionally known in thepapermaking art can be used to dry the intermediate web 25. For example,flow-through dryers, nonthermal, capillary dewatering devices, andYankee dryers, alone and in combination, are satisfactory.

A preferred method of drying the intermediate web 25 is illustrated inFIG. 1. After leaving the vicinity of vacuum box 24, the intermediateweb 25, which is associated with the papermaking belt 10, passes aroundthe papermaking belt return roll 19a and travels in the directionindicated by directional arrow B. The intermediate web 25 then passesthrough optional predryer 26. This predryer 26 can be a conventionalflow-through dryer (hot air dryer) well known to those skilled in theart.

The quantity of water removed in predryer 26 is controlled so thatpredried web 27 exiting the predryer 26 has a consistency of from about30% to about 98%. Predried web 27, which is still associated with thepapermaking belt 10, passes around papermaking belt return roll 19b andtravels to the region of impression nip roll 20.

Seventh Step

The seventh step in the papermaking process is impressing the paper sidenetwork 34a of the papermaking belt 10 of the present invention into thepredried web by interposing the predried web 27 between the papermakingbelt 10 and an impression surface to form an imprinted web ofpapermaking fibers.

If the intermediate web 25 was not subjected to the optional sixthpredrying step, this seventh step will be performed on the intermediateweb 25.

The seventh step is carried out in the machine illustrated in FIG. 1when the predried web 27 then passes through the nip formed between theimpression nip roll 20 and the Yankee drier drum 28. As the predried web27 passes through this nip, the network pattern formed by the paper sidenetwork 34a on the paper-contacting side 11 of the papermaking belt 10is impressed into predried web 27 to form imprinted web 29.

Eighth Step

The eighth step in the papermaking process is drying the imprinted web29. The imprinted web 29 separates from the papermaking belt 10 of thepresent invention after the paper side network 34a is impressed into theweb to from imprinted web 29. As the imprinted web 29 separates from thepapermaking belt 10 of the present invention, it is adhered to thesurface of Yankee dryer drum 28 where it is dried to a consistency of atleast about 95%.

The section of the belt 10 which has been carrying the web passes aroundpapermaking belt 10 return rolls 19c, 19d, 19e, and 19f and throughshowers 102 and 102a located therebetween where it is cleaned. From theshowers, the section of the belt moves on to the emulsion roll 21 whereit receives another application of emulsion 22 prior to contactinganother portion of the embryonic web 18.

Ninth Step

The ninth step in the papermaking process is the foreshortening of thedried web (imprinted web 29). This ninth step is an optional, but highlypreferred, step.

As used herein, foreshortening refers to the reduction in length of adry paper web which occurs when energy is applied to the dry web in sucha way that the length of the web is reduced and the fibers in the webare rearranged with an accompanying disruption of fiber-fiber bonds.Foreshortening can be accomplished in any of several well-known ways.The most common, and preferred, method is creping.

In the creping operation, the dried web 29 is adhered to a surface andthen removed from that surface with a doctor blade 30. As shown in FIG.1, the surface to which the web is usually adhered also functions as adrying surface. Typically, this surface is the surface of a Yankee dryerdrum 28 as shown in FIG. 1.

The adherence of the imprinted web 29 to the surface of Yankee dryerdrum 28 is facilitated by the use of a creping adhesive. Typical crepingadhesives can include any suitable glue, such as those based onpolyvinyl alcohol. Specific examples of suitable adhesives are describedin U.S. Pat. No. 3,926,716 issued to Bates on Dec. 16, 1975,incorporated by reference herein. The adhesive is applied either topredried web 27 immediately prior to its passage through the abovedescribed nip, or more preferably to the surface of Yankee dryer drum 28prior to the point at which the web is pressed against the surface ofYankee dryer drum 28 by the impression nip roll 20. The particular meansof glue application and the technique for applying the glue used in thepractice of the present invention are conventional, and are, therefore,now shown in FIG. 1. Any technique for applying the creping adhesivesknown to those skilled in the art, such as spraying, can be used.

In general, only the nondeflected portions of the web 29 which have beenassociated with paper side network 34a on the paper-contacting side 11of the papermaking belt 10 are directly adhered to the surface of Yankeedryer drum 28. The pattern of the paper side 34a network and itsorientation relative to the doctor blade 30 will in major part dictatethe extent and the character of the creping imparted to the web.

The physical characteristics of the paper web 31 which is made by theprocess of the present invention are described in the aforementionedU.S. Pat. No. 4,529,480 entitled "Tissue Paper", which issued to Trokhanon Jul. 16, 1985, and which is incorporated herein by reference. Thenetwork region and the plurality of domes in the paper web 31, however,will be formed into linear Idaho pattern" rather than in the hexagonpattern shown in the drawings of U.S. Pat. No. 4,529,480 due to thedifference in the shape of conduits in the preferred embodiment of thepapermaking belt 10 of the present invention.

The paper web 31, which is the product of this invention, can beoptionally calendered and is either rewound with or without differentialspeed rewinding or is cut and stacked all by conventional means whichare not illustrated in FIG. 1. The paper web 31 is then ready for use.

4. Test Methods

It has been found that belts with a certain amount of backside texturewill achieve the desired goals of reducing the undesirable accumulationof paper fibers on the surfaces of the vacuum dewatering equipment andcontrolling the other problems associated with the fiber accumulation.The amount and character of backside texturing which must be present forthe desired results to be obtained when using the papermaking belt 10 ofthe present invention is a quality of the belt which is referred to asthe fluid passage capacity of the belt, or more particularly, of thetextured backside surface 12 of the belt. As used herein, the term"fluid passage capacity" refers to a measurement of the air whichtravels (or "air leakage") across the backside 12 of the papermakingbelt 10 under the conditions of the test described below which has beendeveloped for this particular purpose.

The air leakage across the backside 12 of the papermaking belt 10 willhereinafter sometimes be referred to as the "X-Y" air leakage. The "X-Y"language is derived from the fact that if the papermaking belt 10 of thepresent invention were placed in a Cartesian coordinate system with thebackside 12 of the papermaking belt 10 lying in the plane formed by thex and y axes, the air leakage which is of interest would be that whichpasses along the backside 12 surface of the belt 10 in any direction inthe X-Y plane.

The X-Y or backside air leakage test utilizes a device which is depictedschematically in FIGS. 30 and 31. FIG. 30 is a schematic plan view ofthe top surface of the backside leakage testing device 56. All of thehoses and tubing generally associated with the testing device have beenomitted from FIG. 30 for simplicity. These hoses and tubes are best seenin the side view of the device shown in FIG. 31. As shown in thesefigures, the backside leakage testing device 56 has as its basiccomponents, a stand 57, which includes a first plate 58 having a hole 59in the center; a smooth round second plate 60 separate from the stand,which can be placed over the hole 59 in the first plate 58; aliquid-filled vacuum gauge 62; and, a flow meter 63.

In its preferred form, the plate which forms the top of the stand (i.e.,the first plate 58) is square, 8 inches by 8 inches (20.32 cm×20.32 cm),and 1/2 inch (1.27 cm) thick. The first plate 58 provides a flat,nondeformable, and fluid-impervious (i.e., impervious to gases andliquids) surface. It is preferably made of stainless steel with amirrored finish and an extremely smooth surface. It is particularlyimportant that there be no scratches or other defects on the surface ofthis plate to obtain accurate readings. Such surface defects will allowadditional air leakage to occur which will result in higher readingsthan if the first plate 58 did not have such defects. The diameter ofthe hole in the center of this plate is 1.0 inch (2.54 cm). In addition,in the stand used for the test described herein, a circle approximately3.5 inches (8.89 cm) in diameter is inscribed into the first plate 58which is centered around the hole 59. The purpose of this circle is toprovide a guideline for centering the second plate 60 over the hole 59.It is not believed that this circle has an effect on the accuracy of thereadings. The round second plate 60 which is not a part of the stand is,in its preferred form, also made of stainless steel, and is 3 inches(7.62 cm) in diameter, and 1/2 inch (1.27 cm) thick. The second plate 60weighs 405 grams. The weight must be sufficient to retain the sample ofthe belt which is being tested on the stand without unduly compressingthe same.

As shown in FIG. 31, an adapter 61 fits inside the hole 59 in the firstplate 58 so a tube or hose can be inserted into the hole 59 and retainedtherein. The adapter 61 has a short tube 64 which extends from at leastone of its ends. This tube 64 extends toward the opening of the hole 59along the surface of the first plate 58 on which the section of the beltbeing tested rests. The inside diameter of the tube 64 which extendsfrom the adapter 61 is 0.312 inches (0.793 cm).

A hose 65a runs from the other end of the adapter 61 to the bottom of aflow meter 63. The flow meter 63 is used to measure the rate of air flowthrough the portion of the papermaking belt 10 being tested. The flowmeter 63 has a numbered scale which runs between 0 and 150. As with mostflow meters, no specific units are indicated on the scale. Therefore, aswill be described more fully below, the flow meter 63 has beencalibrated to some known unit. A suitable flow meter is one which ismarked FM 102-05 manufactured by the Cole Parmer Company, Chicago, Ill.60648.

Another hose 65b runs from the top of the flow meter 63 to a tube 68which is ultimately connected to a vacuum source which pulls a vacuum inthe direction of the arrow V_(T). The vacuum source itself isconventional, and is, therefore, not shown in FIG. 31. There are severalbranches of the tube 68 which runs from the hose 65b to the vacuumsource. Included on these branches are a shut-off valve 69a, a coarseadjustment valve 69b, and a fine adjustment valve 69c, as well as theliquid-filled vacuum gauge 62 which is calibrated for pressures ofbetween 0 and 30 inches (0-76.2 cm) of mercury. Any gauge whichaccurately measures vacuum in inches of mercury is suitable. An exampleof such a vacuum gauge is a model which is marked AISI 316 Tube & socketNo. 250.2274A manufactured under the trademark Ashcroft Duragauge inStratford, Conn.

In operation, a section of the papermaking belt 10 is placed across thetop of the hole 59 in the plate 58 of the X-Y leakage test stand 57. Thesection of the papermaking belt 10 is placed on the plate 58 with itspaper-contacting side 11 up (i.e., facing away from the plate 58) andits backside 12 directly on the plate 58. The section of the papermakingbelt 10 should be sufficient in size so that it is at least larger thanthe round second plate 60 in all dimensions. Only a portion of the pieceof the papermaking belt 10 is shown in FIGS. 30 and 31, however, forpurposes of illustration. In addition, it should also be noted that forpurposes of illustration, the portion of the papermaking belt 10 shownin these figures has been greatly exaggerated relative to the size ofthe leakage tester 56.

The second plate 60 is then placed on top of the paper-contacting side11 of the papermaking belt 10 to hold the belt in place and to cover theconduits 36 of the portion of the papermaking belt 10 being tested toprevent the air from entering through the conduits 36. Vacuum pressureis applied and the valves 69a, 69b, and 69c are adjusted so that thepressure differential measured by the vacuum gauge 62 is preset atapproximately 7 inches (17.78 cm) of mercury. Readings have, however,been taken when the vacuum gauge 62 was preset at 5 inches (12.7 cm) ofmercury before a completely standardized procedure was established. Thereadings taken at 5 inches (12.7 cm) of mercury can be converted toreadings taken at 7 inches of mercury by inserting the readings taken at5 inches (12.7 cm) of mercury into the following equation where x is thereading taken at 5 inches (12.7 cm) of mercury and y is thecorresponding reading at 7 inches (17.7 cm) of mercury:

    y=2.6720+1.2361x

When vacuum pressure has thus been applied, a direct reading is taken onthe flow meter 63. The number which is read directly from the flow meter63 is a measure of the X-Y leakage across the backside 12 of the sectionof the papermaking belt 10, or more particularly, of the volume of airwhich enters around the circumference of the second plate 60 (such as inthe direction indicated by arrows L) and moves across the backside 12 ofthe section of the papermaking belt 10 being tested. The units of thisreading have been named "Marlatts" after Henry Marlatt of Mehoopany,Pa., an individual responsible for obtaining some of the readings of airleakage using the above-described test. A conversion from Marlatts intostandard cubic centimeters/minute can be made by inserting the readingmeasured in Marlatts into the following equation where x is the readingin Marlatts and y is the corresponding value in standard cc/minute:

    y=36.085+52.583x-0.07685x.sup.2.

This equation for converting Marlatts into standard cc/min. wasdeveloped by calibrating the flow meter to standard cc/min. using a BuckOptical Soap Bubble Meter. The relationship between the direct readingstaken on the flow meter 63 in Marlatts and the corresponding reading instandard cc/min is depicted graphically in FIG. 32.

Preferably, the fluid passage capacity (or amount of air leakagemeasured using the test described above) should not be less than about35 Marlatts (approximately 1,800 standard cc/min.). Belts having a fluidpassage capacity of 35 Marlatts begin to achieve some of the benefits ofreducing the accumulation of paper fibers in the vacuum dewateringequipment used in the papermaking process. In other words, thepassageways 37 in the second surface 35 of the framework 32, togetherwith the other elements which comprise the backside texture, should besufficient in size, or capacity, to permit at least about 1,800 standardcc/min. of air or other fluid to travel (or escape) across the texturedbackside surface of the belt when the backside 12 of the belt 10 isplaced in contact with a flat, nondeformable, fluid-impervious surfaceand the conduits 36 are covered to prevent the air or fluid fromescaping through the conduits 36, and a fluid pressure differential ofapproximately 7 inches (17.78 cm) of mercury less than atmosphericpressure is applied to the backside 12 of the belt 10.

The amount of air leakage which is present in papermaking belts whichwill perform at an acceptable level in the papermaking process is an airleakage of generally greater than approximately 40 Marlatts(approximately 2,000 standard cc/min.) at 450-550 cfm air permeability,the preferred minimum range of air permeabilities for the compositebelt. Preferably, a belt should have an air leakage reading of at leastapproximately 70 Marlatts (approximately 3,300 standard cc/min.), andmost preferably, the belt should have an air leakage reading of at leastapproximately 100 Marlatts (approximately 4,500 cc/min) under the sameconditions (450-550 cfm air permeability).

The upper limit on the desirable amount of backside texturing is thatamount of texturing which would permits the maximum amount of air totravel across the backside 12 of the papermaking belt 10 without theundesirable result of decreasing the vacuum pressure differential belowthat amount necessary to cause the fibers of the paper web to bedeflected into the conduits 36 of the papermaking belt 10. It isbelieved that this amount could be as great as 250 Marlatts(approximately 8,400 standard cc/min.), or more.

FIGS. 34A-C are enlarged photographs of an example of a papermaking belt10 made according to the process of the present invention. Thephotograph of the belt shown in FIGS. 34A-C can be compared to thephotographs of the prior smooth backsided belt shown in FIGS. 33A and B.

Several matters should be noted when examining the enlarged photographsof these belts. First, it should be apparent that due to the level ofmagnification used, the portions of the belts shown in the photographsare generally very small portions of those belts. The portions of thebelts which are shown in the photographs (and particularly the backsidetexturing on those belts) are believed to be fairly representative ofthe characteristics of the entire belt. This does not mean, however,that sections of the belt which are more representative of the overallcharacteristics of the entire belt than the portions of the beltsdepicted in the photographs, do not exist.

In addition, it should be noted that the portions of the belts shown inthe photographs will more than likely not correspond identically withthe portions of the belt shown in the other photographs taken fromdifferent angles due to the difficulty of examining and photographingthe minute features of such an article under magnification. In otherwords, the portions of the belt which form the paper-contacting side 11and the backside 12 may not actually lie directly above and below eachother in the belt 10. Likewise, the cross-section photograph of the beltmay not be a cross-section of the same portion of the belt shown in thetop and bottom side photographs. With this is mind, the enlargedphotographs of the belts will now be examined.

FIGS. 33A and 33B are plan view photographs, each enlarged about 25times actual size, of the paper-contacting side 11a and the backside12a, respectively, of a papermaking belt 10a which does not contain theimprovements disclosed herein. The belt shown in FIGS. 33A and 33Bdiffers somewhat in dimensions from the belt formed by the process ofthe present invention because the belt shown in FIGS. 33A and 33B is a711 linear Idaho belt. The belt shown in FIGS. 33A and B, therefore, hassmaller-sized conduits 36, and a greater number of conduits per squareinch. The belt 10a shown in FIGS. 33A and B also differs in that it hasa monolayer reinforcing structure.

The backside 12a of the belt 10a shown in FIG. 33B shows one of theproblems which occurred in casting belts having smaller conduits. Theconduits 36 tended to close up on the backside 12a. Ideally, thebackside 12a of the belt 10a in FIG. 33B should appear nearly identicalto the paper-contacting side 11a shown in FIG. 33A. If the walls 44 ofthe conduits 36 are tapered, in the backside the conduits should appearsmaller and the area of the backside network surface should be greater.The departure from the hypothetical ideal belt is also caused partiallyby minor imperfections in the belt which appeared to be greatlyexaggerated in these photographs. When backside 12 of the belt 10a shownin FIG. 1B is examined macroscopically, the conduit openings in thebackside 12a of the belt 10a appear to be very similar to the conduitopenings in the paper-contacting side 11a of the belt 10a. However, suchan examination of the belt 10a reveals that a very thin film of resinousmaterial covers the conduits which may at least partially account forthe differences in the appearance of the backside 12a of the belt 10a.

The photographs of the belt 10 shown in FIGS. 34A-C depict a 300 linearIdaho 35% knuckle area belt which was made in accordance with theprocess of the present invention. The backside texture of the belt shownin these figures was created by giving all of the warp yarns 53 in thesecond warp layer D a first opacity O₁. The first opacity O₁ wasprovided to the warp yarns 53 in the second warp layer D by coating theindividual yarns with an organic dye. More specifically, the coating wasapplied with a black ink marking pen. All of the photographs have beenenlarged about 25 times the actual size of the belt 10. FIG. 34A is aphotograph of the paper-contacting side 11 of the belt 10 taken at anangle of approximately 35 degrees relative to an imaginary line drawnnormal to the surface of the paper-contacting side (i.e., relative tothe z-direction). FIG. 34B is a photograph of the backside 12 of thebelt 10 shown in FIG. 34A. FIG. 34C is a cross-machine directionsectional view of the belt 10 shown in FIGS. 34A and 34B.

FIG. 34A shows that the paper side network (upon which the paper webwill be carried) is macroscopically monoplanar, patterned andcontinuous, As show in FIG. 34A, the paper side network 34a is alsomicroscopically monoplanar, patterned and continuous at the level ofmagnification at which the photograph was taken. The paper side network34a surrounds and defines the openings 42 of a plurality of conduits 36into which the fibers in the embryonic web 18 can be deflected andrearranged into the form of the improved paper web. The reinforcingstructure 33 can be seen in the holes or openings 41 found by theconduits 36. The reinforcing structure 33 is comprised of a plurality ofmachine direction warp yarns 53 which are interwoven with a plurality ofcross-machine direction weft yarns 54 to leave interstices 39therebetween. The reinforcing structure 33 is the preferred multilayerreinforcing structure which has vertically stacked warp yarns 53. Asshown in FIG. 34A, the interstices 39 are generally several timessmaller than the conduits 36. The reinforcing structure 33 strengthensthe framework 32 without interfering with the drainage of water and thepassage of air through the conduits 36.

The backside 12 of the belt 10 is shown in FIG. 34B and 34C. FIGS. 34Band 34C shows the backside texturing which is formed by the process ofthe present invention. As shown in FIGS. 34B and 34C, the backsidenetwork 35a is discontinuous. Without the backside texturing formed bythe process of the present invention, the backside network 35a wouldappear very similar to the paper side network 34a.

In FIG. 34B, the backside texturing produced by the process of thepresent invention comprises passageways 37 that provide surface textureirregularities 38 in the backside network 35a of the framework 32. Thebackside texture appears as a plurality of discontinuities in thebackside network 35a. These discontinuities comprise the passageways 37.The passageways 37 are distributed fairly regularly and in a generalpattern. The passageways 37 are positioned predominately over the warpyarns 53 which comprise the first portion P₀₁ of the reinforcingstructure 33 (in other words, in the projected warp areas). When thefirst portion P₀₁ comprises the warp yarns 53 in the second warp layerD, the first projected area A₁ and the projected warp area will be thesame.

FIG. 34B also shows that a multiplicity of the passageways 37 arepositioned in and adjacent to the projected machine side weft knuckleareas A_(kwt2) and adjacent the knuckles 105b₂ formed in themachine-facing side 52 of the reinforcing structure 33 by the weft yarns54. This is believed to be due at least in part to the fact that themachine side weft knuckles 105b₂ comprise the portion of the reinforcingstructure 33 which is in direct contact with the working surface of theforming unit during the casting process, and as a result, no resinousmaterial will lie between these knuckles and the working surface. Thiscauses these knuckles to be exposed in the finished belt 10.

FIG. 34C shows that the heights of the passageways 37 extend inward fromthe plane defined by the machine-facing side of the reinforcingstructure P_(k2) to the bottom sides of the structural components 40awhich comprise the opaque first portion P₀₁.

While particular embodiments of the present invention have beenillustrated and described, it would be obvious to those skilled in theart that various other changes and modifications can be made withoutdeparting from the spirit and scope of the invention. It is thereforeintended to cover in the appended claims all such changes andmodifications that are within the scope of this invention.

What is claimed is:
 1. A papermaking belt having a paper-contacting sideand a textured backside opposite said paper-contacting side, saidpapermaking belt comprising:a framework comprising a curedphotosensitive resinous material, said framework having a first surfacedefining said paper-contacting side of said belt, a second surfaceopposite said first surface, and conduits extending between said firstsurface and said second surface, said first surface having a paper sidenetwork formed therein defining said conduits, and said second surfacehaving a backside network with passageways, distinct from said conduits,that provide surface texture irregularities in said backside network; areinforcing structure positioned between said first surface and at leasta portion of said second surface, said reinforcing structure having apaper-facing side, a machine-facing side opposite said paper-facingside, interstices, and a reinforcing component comprised of a pluralityof structural components, a first portion of said reinforcing componenthaving a first opacity and a second portion of said reinforcingcomponent having a second opacity less than said first opacity, whereinsaid first opacity is sufficient to substantially prevent curing of saidphotosensitive resinous material which comprises the framework when saidphotosensitive resinous material is in its uncured state and said firstportion is positioned between said photosensitive resinous material andan actinic light source, and said second opacity is sufficient to permitcuring of said photosensitive resinous material, said first portiondefining a first projected area; wherein said passageways in saidbackside network of said framework are positioned predominately withinsaid first projected area; wherein said reinforcing structure comprisesa plurality of machine-direction warp yarns interwoven with a pluralityof cross-machine direction weft yarns to form said interstices betweensaid warp yarns and said weft yarns, a plurality of said warp yarns orsaid weft yarns having a first opacity and a plurality of said warpyarns or said weft yarns having good second opacity, said first yarnsand said second yarns being of substantially equal diameter.
 2. Thepapermaking belt of claim 1 wherein at least some of said warp yarnshave said first opacity.
 3. The papermaking belt of claim 2 whereinevery alternating yarn of said warp yarns has said first opacity.
 4. Thepapermaking belt of claim 2 wherein every warp yarn has said firstopacity.
 5. The papermaking belt of claim 1 wherein said reinforcingstructure comprises a multilayer woven element, said machine-directionwarp yarns being disposed in a first layer and in a second layer, saidwarp yarns in said first and second layers being arranged in a generallyvertically stacked relationship with each other, said first layer ofsaid warp yarns together with said interwoven weft yarns forming saidpaper-facing side of said reinforcing structure, and said second layerof said warp yarns together with said interwoven weft yarns forming saidmachine-facing side of said reinforcing structure.
 6. The papermakingbelt of claim 5 wherein at least some of said warp yarns in said secondlayer have said first opacity.
 7. The papermaking belt of claim 6wherein every alternating yarn of said warp yarns in said second layerhas said first opacity.
 8. The papermaking belt of claim 6 wherein everywarp yarn in said second layer has said first opacity.
 9. Thepapermaking belt of claim 1 wherein said first portion comprises atleast one structural component which is at least partially comprised ofan opaque material.
 10. The papermaking belt of claim 9 wherein saidopaque material is opaque to light having a wavelength of between about200 and about 400 nanometers.
 11. The papermaking belt of claim 1wherein said first portion comprises an opaque coating which has beenapplied to said machine-facing side of said reinforcing structure. 12.The papermaking belt of claim 11 wherein said opaque coating comprises amaterial which is opaque to light having a wavelength of between about200 and about 400 nanometers.
 13. A woven papermaking fabric useful in apapermaking machine, which fabric comprises:a plurality of yarns, saidplurality of yarns comprising a plurality of machine-direction warpyarns interwoven with a plurality of cross-machine direction weft yarnsto form interstices therebetween, a portion of said plurality of yarnshas a first opacity and a portion of said yarns has a second opacity,said first opacity being greater than said second opacity, said yarnshaving said first opacity and said yarns having said second opacitybeing of substantially equal diameter.
 14. The papermaking fabric ofclaim 13 wherein at least some of said warp yarns have said firstopacity.
 15. The papermaking fabric of claim 14 wherein everyalternating yarn of said warp yarns has said first opacity.
 16. Thepapermaking fabric of claim 14 wherein every warp yarn has said firstopacity.
 17. The papermaking fabric of claim 13 wherein said wovenpapermaking fabric comprises a multilayer woven element, saidmachine-direction warp yarns being disposed in a first layer and in asecond layer, said warp yarns in said first and second layers beingarranged in a generally vertically stacked relationship with each other,said first layer of said warp yarns together with said interwoven weftyarns forming said paper-facing side of said reinforcing structure, andsaid second layer of said warp yarns together with said interwoven weftyarns forming said machine-facing side of said papermaking fabric. 18.The papermaking fabric of claim 17 wherein at least some of said warpyarns in said second layer have said first opacity.
 19. The papermakingfabric of claim 18 wherein every alternating yarn of said warp yarns insaid second layer has said first opacity.
 20. The papermaking fabric ofclaim 18 wherein every warp yarn in said second layer has said firstopacity.